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2022-05-19kernfs: Separate kernfs_pr_cont_buf and rename_lock.Hao Luo1-12/+19
Previously the protection of kernfs_pr_cont_buf was piggy backed by rename_lock, which means that pr_cont() needs to be protected under rename_lock. This can cause potential circular lock dependencies. If there is an OOM, we have the following call hierarchy: -> cpuset_print_current_mems_allowed() -> pr_cont_cgroup_name() -> pr_cont_kernfs_name() pr_cont_kernfs_name() will grab rename_lock and call printk. So we have the following lock dependencies: kernfs_rename_lock -> console_sem Sometimes, printk does a wakeup before releasing console_sem, which has the dependence chain: console_sem -> p->pi_lock -> rq->lock Now, imagine one wants to read cgroup_name under rq->lock, for example, printing cgroup_name in a tracepoint in the scheduler code. They will be holding rq->lock and take rename_lock: rq->lock -> kernfs_rename_lock Now they will deadlock. A prevention to this circular lock dependency is to separate the protection of pr_cont_buf from rename_lock. In principle, rename_lock is to protect the integrity of cgroup name when copying to buf. Once pr_cont_buf has got its content, rename_lock can be dropped. So it's safe to drop rename_lock after kernfs_name_locked (and kernfs_path_from_node_locked) and rely on a dedicated pr_cont_lock to protect pr_cont_buf. Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Hao Luo <haoluo@google.com> Link: https://lore.kernel.org/r/20220516190951.3144144-1-haoluo@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-05-06kernfs: Rename kernfs_put_open_node to kernfs_unlink_open_file.Imran Khan1-9/+19
Since we are no longer using refcnt for kernfs_open_node instances, rename kernfs_put_open_node to kernfs_unlink_open_file to reflect this change. Also update function description and inline comments accordingly. Signed-off-by: Imran Khan <imran.f.khan@oracle.com> Link: https://lore.kernel.org/r/20220504095123.295859-2-imran.f.khan@oracle.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-05-02Merge 5.18-rc5 into driver-core-nextGreg Kroah-Hartman1-1/+6
We need the kernfs/driver core fixes in here as well. Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-04-27kernfs: fix NULL dereferencing in kernfs_removeMinchan Kim1-1/+6
kernfs_remove supported NULL kernfs_node param to bail out but revent per-fs lock change introduced regression that dereferencing the param without NULL check so kernel goes crash. This patch checks the NULL kernfs_node in kernfs_remove and if so, just return. Quote from bug report by Jirka ``` The bug is triggered by running NAS Parallel benchmark suite on SuperMicro servers with 2x Xeon(R) Gold 6126 CPU. Here is the error log: [ 247.035564] BUG: kernel NULL pointer dereference, address: 0000000000000008 [ 247.036009] #PF: supervisor read access in kernel mode [ 247.036009] #PF: error_code(0x0000) - not-present page [ 247.036009] PGD 0 P4D 0 [ 247.036009] Oops: 0000 [#1] PREEMPT SMP PTI [ 247.058060] CPU: 1 PID: 6546 Comm: umount Not tainted 5.16.0393c3714081a53795bbff0e985d24146def6f57f+ #16 [ 247.058060] Hardware name: Supermicro Super Server/X11DDW-L, BIOS 2.0b 03/07/2018 [ 247.058060] RIP: 0010:kernfs_remove+0x8/0x50 [ 247.058060] Code: 4c 89 e0 5b 5d 41 5c 41 5d 41 5e c3 49 c7 c4 f4 ff ff ff eb b2 66 66 2e 0f 1f 84 00 00 00 00 00 66 90 0f 1f 44 00 00 41 54 55 <48> 8b 47 08 48 89 fd 48 85 c0 48 0f 44 c7 4c 8b 60 50 49 83 c4 60 [ 247.058060] RSP: 0018:ffffbbfa48a27e48 EFLAGS: 00010246 [ 247.058060] RAX: 0000000000000001 RBX: ffffffff89e31f98 RCX: 0000000080200018 [ 247.058060] RDX: 0000000080200019 RSI: fffff6760786c900 RDI: 0000000000000000 [ 247.058060] RBP: ffffffff89e31f98 R08: ffff926b61b24d00 R09: 0000000080200018 [ 247.122048] R10: ffff926b61b24d00 R11: ffff926a8040c000 R12: ffff927bd09a2000 [ 247.122048] R13: ffffffff89e31fa0 R14: dead000000000122 R15: dead000000000100 [ 247.122048] FS: 00007f01be0a8c40(0000) GS:ffff926fa8e40000(0000) knlGS:0000000000000000 [ 247.122048] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 247.122048] CR2: 0000000000000008 CR3: 00000001145c6003 CR4: 00000000007706e0 [ 247.122048] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 247.122048] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 247.122048] PKRU: 55555554 [ 247.122048] Call Trace: [ 247.122048] <TASK> [ 247.122048] rdt_kill_sb+0x29d/0x350 [ 247.122048] deactivate_locked_super+0x36/0xa0 [ 247.122048] cleanup_mnt+0x131/0x190 [ 247.122048] task_work_run+0x5c/0x90 [ 247.122048] exit_to_user_mode_prepare+0x229/0x230 [ 247.122048] syscall_exit_to_user_mode+0x18/0x40 [ 247.122048] do_syscall_64+0x48/0x90 [ 247.122048] entry_SYSCALL_64_after_hwframe+0x44/0xae [ 247.122048] RIP: 0033:0x7f01be2d735b ``` Link: https://bugzilla.kernel.org/show_bug.cgi?id=215696 Link: https://lore.kernel.org/lkml/CAE4VaGDZr_4wzRn2___eDYRtmdPaGGJdzu_LCSkJYuY9BEO3cw@mail.gmail.com/ Fixes: 393c3714081a (kernfs: switch global kernfs_rwsem lock to per-fs lock) Cc: stable@vger.kernel.org Reported-by: Jirka Hladky <jhladky@redhat.com> Tested-by: Jirka Hladky <jhladky@redhat.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Minchan Kim <minchan@kernel.org> Link: https://lore.kernel.org/r/20220427172152.3505364-1-minchan@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-04-27kernfs: Remove reference counting for kernfs_open_node.Imran Khan1-14/+9
The decision to free kernfs_open_node object in kernfs_put_open_node can be taken based on whether kernfs_open_node->files list is empty or not. As far as kernfs_drain_open_files is concerned it can't overlap with kernfs_fops_open and hence can check for ->attr.open optimistically (if ->attr.open is NULL) or under kernfs_open_file_mutex (if it needs to traverse the ->files list.) Thus kernfs_drain_open_files can work w/o ref counting involved kernfs_open_node as well. So remove ->refcnt and modify the above mentioned users accordingly. Suggested by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Imran Khan <imran.f.khan@oracle.com> Link: https://lore.kernel.org/r/20220324103040.584491-2-imran.f.khan@oracle.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-04-02Merge branch 'work.misc' of ↵Linus Torvalds1-6/+1
git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs Pull vfs updates from Al Viro: "Assorted bits and pieces" * 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: aio: drop needless assignment in aio_read() clean overflow checks in count_mounts() a bit seq_file: fix NULL pointer arithmetic warning uml/x86: use x86 load_unaligned_zeropad() asm/user.h: killed unused macros constify struct path argument of finish_automount()/do_add_mount() fs: Remove FIXME comment in generic_write_checks()
2022-03-18kernfs: fix typos in commentsJulia Lawall1-1/+1
Various spelling mistakes in comments. Detected with the help of Coccinelle. Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr> Link: https://lore.kernel.org/r/20220314115354.144023-5-Julia.Lawall@inria.fr Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-02-23kernfs: move struct kernfs_root out of the public view.Greg Kroah-Hartman2-0/+27
There is no need to have struct kernfs_root be part of kernfs.h for the whole kernel to see and poke around it. Move it internal to kernfs code and provide a helper function, kernfs_root_to_node(), to handle the one field that kernfs users were directly accessing from the structure. Cc: Imran Khan <imran.f.khan@oracle.com> Acked-by: Tejun Heo <tj@kernel.org> Link: https://lore.kernel.org/r/20220222070713.3517679-1-gregkh@linuxfoundation.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-02-22kernfs: remove redundant kernfs_rwsem declaration.Imran Khan1-1/+0
Since 'commit 393c3714081a ("kernfs: switch global kernfs_rwsem lock to per-fs lock")' per-fs kernfs_rwsem has replaced global kernfs_rwsem. Remove redundant declaration of global kernfs_rwsem. Fixes: 393c3714081a ("kernfs: switch global kernfs_rwsem lock to per-fs lock") Signed-off-by: Imran Khan <imran.f.khan@oracle.com> Link: https://lore.kernel.org/r/20220218010205.717582-1-imran.f.khan@oracle.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-02-01seq_file: fix NULL pointer arithmetic warningMaíra Canal1-6/+1
Implement conditional logic in order to replace NULL pointer arithmetic. The use of NULL pointer arithmetic was pointed out by clang with the following warning: fs/kernfs/file.c:128:15: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] return NULL + !*ppos; ~~~~ ^ fs/seq_file.c:559:14: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] return NULL + (*pos == 0); Signed-off-by: Maíra Canal <maira.canal@usp.br> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2021-12-03kernfs: prevent early freeing of root nodeMinchan Kim1-1/+7
Marek reported the warning below. ========================= WARNING: held lock freed! 5.16.0-rc2+ #10984 Not tainted ------------------------- kworker/1:0/18 is freeing memory ffff00004034e200-ffff00004034e3ff, with a lock still held there! ffff00004034e348 (&root->kernfs_rwsem){++++}-{3:3}, at: __kernfs_remove+0x310/0x37c 3 locks held by kworker/1:0/18: #0: ffff000040107938 ((wq_completion)cgroup_destroy){+.+.}-{0:0}, at: process_one_work+0x1f0/0x6f0 #1: ffff80000b55bdc0 ((work_completion)(&(&css->destroy_rwork)->work)){+.+.}-{0:0}, at: process_one_work+0x1f0/0x6f0 #2: ffff00004034e348 (&root->kernfs_rwsem){++++}-{3:3}, at: __kernfs_remove+0x310/0x37c stack backtrace: CPU: 1 PID: 18 Comm: kworker/1:0 Not tainted 5.16.0-rc2+ #10984 Hardware name: Raspberry Pi 4 Model B (DT) Workqueue: cgroup_destroy css_free_rwork_fn Call trace: dump_backtrace+0x0/0x1ac show_stack+0x18/0x24 dump_stack_lvl+0x8c/0xb8 dump_stack+0x18/0x34 debug_check_no_locks_freed+0x124/0x140 kfree+0xf0/0x3a4 kernfs_put+0x1f8/0x224 __kernfs_remove+0x1b8/0x37c kernfs_destroy_root+0x38/0x50 css_free_rwork_fn+0x288/0x3d4 process_one_work+0x288/0x6f0 worker_thread+0x74/0x470 kthread+0x188/0x194 ret_from_fork+0x10/0x20 Since kernfs moves the kernfs_rwsem lock into root, it couldn't hold the lock when the root node is tearing down. Thus, get the refcount of root node. Fixes: 393c3714081a ("kernfs: switch global kernfs_rwsem lock to per-fs lock") Reported-by: Marek Szyprowski <m.szyprowski@samsung.com> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Minchan Kim <minchan@kernel.org> Link: https://lore.kernel.org/r/20211201231648.1027165-1-minchan@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-11-24kernfs: switch global kernfs_rwsem lock to per-fs lockMinchan Kim5-63/+95
The kernfs implementation has big lock granularity(kernfs_rwsem) so every kernfs-based(e.g., sysfs, cgroup) fs are able to compete the lock. It makes trouble for some cases to wait the global lock for a long time even though they are totally independent contexts each other. A general example is process A goes under direct reclaim with holding the lock when it accessed the file in sysfs and process B is waiting the lock with exclusive mode and then process C is waiting the lock until process B could finish the job after it gets the lock from process A. This patch switches the global kernfs_rwsem to per-fs lock, which put the rwsem into kernfs_root. Suggested-by: Tejun Heo <tj@kernel.org> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Minchan Kim <minchan@kernel.org> Link: https://lore.kernel.org/r/20211118230008.2679780-1-minchan@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-10-18Merge 5.15-rc6 into driver-core-nextGreg Kroah-Hartman1-1/+8
We need the driver-core fixes in here as well. Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-10-05fs/kernfs/symlink.c: replace S_IRWXUGO with 0777 on kernfs_create_link()Luis Chamberlain1-2/+1
If one ends up extending this line checkpatch will complain about the use of S_IRWXUGO suggesting it is not preferred and that 0777 should be used instead. Take the tip from checkpatch and do that change before we do our subsequent changes. This makes no functional changes. Signed-off-by: Luis Chamberlain <mcgrof@kernel.org> Link: https://lore.kernel.org/r/20210927163805.808907-8-mcgrof@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-10-04kernfs: don't create a negative dentry if inactive node existsIan Kent1-1/+8
It's been reported that doing stress test for module insertion and removal can result in an ENOENT from libkmod for a valid module. In kernfs_iop_lookup() a negative dentry is created if there's no kernfs node associated with the dentry or the node is inactive. But inactive kernfs nodes are meant to be invisible to the VFS and creating a negative dentry for these can have unexpected side effects when the node transitions to an active state. The point of creating negative dentries is to avoid the expensive alloc/free cycle that occurs if there are frequent lookups for kernfs attributes that don't exist. So kernfs nodes that are not yet active should not result in a negative dentry being created so when they transition to an active state VFS lookups can create an associated dentry is a natural way. It's also been reported that https://github.com/osandov/blktests.git test block/001 hangs during the test. It was suggested that recent changes to blktests might have caused it but applying this patch resolved the problem without change to blktests. Fixes: c7e7c04274b1 ("kernfs: use VFS negative dentry caching") Tested-by: Yi Zhang <yi.zhang@redhat.com> ACKed-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Ian Kent <raven@themaw.net> Link: https://lore.kernel.org/r/163330943316.19450.15056895533949392922.stgit@mickey.themaw.net Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-09-28kernfs: also call kernfs_set_rev() for positive dentryHou Tao1-2/+7
A KMSAN warning is reported by Alexander Potapenko: BUG: KMSAN: uninit-value in kernfs_dop_revalidate+0x61f/0x840 fs/kernfs/dir.c:1053 kernfs_dop_revalidate+0x61f/0x840 fs/kernfs/dir.c:1053 d_revalidate fs/namei.c:854 lookup_dcache fs/namei.c:1522 __lookup_hash+0x3a6/0x590 fs/namei.c:1543 filename_create+0x312/0x7c0 fs/namei.c:3657 do_mkdirat+0x103/0x930 fs/namei.c:3900 __do_sys_mkdir fs/namei.c:3931 __se_sys_mkdir fs/namei.c:3929 __x64_sys_mkdir+0xda/0x120 fs/namei.c:3929 do_syscall_x64 arch/x86/entry/common.c:51 It seems a positive dentry in kernfs becomes a negative dentry directly through d_delete() in vfs_rmdir(). dentry->d_time is uninitialized when accessing it in kernfs_dop_revalidate(), because it is only initialized when created as negative dentry in kernfs_iop_lookup(). The problem can be reproduced by the following command: cd /sys/fs/cgroup/pids && mkdir hi && stat hi && rmdir hi && stat hi A simple fixes seems to be initializing d->d_time for positive dentry in kernfs_iop_lookup() as well. The downside is the negative dentry will be revalidated again after it becomes negative in d_delete(), because the revison of its parent must have been increased due to its removal. Alternative solution is implement .d_iput for kernfs, and assign d_time for the newly-generated negative dentry in it. But we may need to take kernfs_rwsem to protect again the concurrent kernfs_link_sibling() on the parent directory, it is a little over-killing. Now the simple fix is chosen. Link: https://marc.info/?l=linux-fsdevel&m=163249838610499 Fixes: c7e7c04274b1 ("kernfs: use VFS negative dentry caching") Reported-by: Alexander Potapenko <glider@google.com> Signed-off-by: Hou Tao <houtao1@huawei.com> Link: https://lore.kernel.org/r/20210928140750.1274441-1-houtao1@huawei.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-07-27kernfs: dont call d_splice_alias() under kernfs node lockIan Kent1-4/+2
The call to d_splice_alias() in kernfs_iop_lookup() doesn't depend on any kernfs node so there's no reason to hold the kernfs node lock when calling it. Reviewed-by: Miklos Szeredi <mszeredi@redhat.com> Signed-off-by: Ian Kent <raven@themaw.net> Link: https://lore.kernel.org/r/162642772000.63632.10672683419693513226.stgit@web.messagingengine.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-07-27kernfs: use i_lock to protect concurrent inode updatesIan Kent2-8/+14
The inode operations .permission() and .getattr() use the kernfs node write lock but all that's needed is the read lock to protect against partial updates of these kernfs node fields which are all done under the write lock. And .permission() is called frequently during path walks and can cause quite a bit of contention between kernfs node operations and path walks when the number of concurrent walks is high. To change kernfs_iop_getattr() and kernfs_iop_permission() to take the rw sem read lock instead of the write lock an additional lock is needed to protect against multiple processes concurrently updating the inode attributes and link count in kernfs_refresh_inode(). The inode i_lock seems like the sensible thing to use to protect these inode attribute updates so use it in kernfs_refresh_inode(). The last hunk in the patch, applied to kernfs_fill_super(), is possibly not needed but taking the lock was present originally. I prefer to continue to take it to protect against a partial update of the source kernfs fields during the call to kernfs_refresh_inode() made by kernfs_get_inode(). Reviewed-by: Miklos Szeredi <mszeredi@redhat.com> Signed-off-by: Ian Kent <raven@themaw.net> Link: https://lore.kernel.org/r/162642771474.63632.16295959115893904470.stgit@web.messagingengine.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-07-27kernfs: switch kernfs to use an rwsemIan Kent6-70/+71
The kernfs global lock restricts the ability to perform kernfs node lookup operations in parallel during path walks. Change the kernfs mutex to an rwsem so that, when opportunity arises, node searches can be done in parallel with path walk lookups. Reviewed-by: Miklos Szeredi <mszeredi@redhat.com> Signed-off-by: Ian Kent <raven@themaw.net> Link: https://lore.kernel.org/r/162642770946.63632.2218304587223241374.stgit@web.messagingengine.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-07-27kernfs: use VFS negative dentry cachingIan Kent1-20/+35
If there are many lookups for non-existent paths these negative lookups can lead to a lot of overhead during path walks. The VFS allows dentries to be created as negative and hashed, and caches them so they can be used to reduce the fairly high overhead alloc/free cycle that occurs during these lookups. Use the kernfs node parent revision to identify if a change has been made to the containing directory so that the negative dentry can be discarded and the lookup redone. Reviewed-by: Miklos Szeredi <mszeredi@redhat.com> Signed-off-by: Ian Kent <raven@themaw.net> Link: https://lore.kernel.org/r/162642770420.63632.15791924970508867106.stgit@web.messagingengine.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-07-27kernfs: add a revision to identify directory node changesIan Kent2-0/+21
Add a revision counter to kernfs directory nodes so it can be used to detect if a directory node has changed during negative dentry revalidation. There's an assumption that sizeof(unsigned long) <= sizeof(pointer) on all architectures and as far as I know that assumption holds. So adding a revision counter to the struct kernfs_elem_dir variant of the kernfs_node type union won't increase the size of the kernfs_node struct. This is because struct kernfs_elem_dir is at least sizeof(pointer) smaller than the largest union variant. It's tempting to make the revision counter a u64 but that would increase the size of kernfs_node on archs where sizeof(pointer) is smaller than the revision counter. Reviewed-by: Miklos Szeredi <mszeredi@redhat.com> Signed-off-by: Ian Kent <raven@themaw.net> Link: https://lore.kernel.org/r/162642769895.63632.8356662784964509867.stgit@web.messagingengine.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-07-05Merge tag 'driver-core-5.14-rc1' of ↵Linus Torvalds1-43/+43
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core Pull driver core changes from Greg KH: "Here is the small set of driver core and debugfs updates for 5.14-rc1. Included in here are: - debugfs api cleanups (touched some drivers) - devres updates - tiny driver core updates and tweaks Nothing major in here at all, and all have been in linux-next for a while with no reported issues" * tag 'driver-core-5.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: (27 commits) docs: ABI: testing: sysfs-firmware-memmap: add some memmap types. devres: Enable trace events devres: No need to call remove_nodes() when there none present devres: Use list_for_each_safe_from() in remove_nodes() devres: Make locking straight forward in release_nodes() kernfs: move revalidate to be near lookup drivers/base: Constify static attribute_group structs firmware_loader: remove unneeded 'comma' macro devcoredump: remove contact information driver core: Drop helper devm_platform_ioremap_resource_wc() component: Rename 'dev' to 'parent' component: Drop 'dev' argument to component_match_realloc() device property: Don't check for NULL twice in the loops driver core: auxiliary bus: Fix typo in the docs drivers/base/node.c: make CACHE_ATTR define static DEVICE_ATTR_RO debugfs: remove return value of debugfs_create_ulong() debugfs: remove return value of debugfs_create_bool() scsi: snic: debugfs: remove local storage of debugfs files b43: don't save dentries for debugfs b43legacy: don't save dentries for debugfs ...
2021-06-29fs: move ramfs_aops to libfsChristoph Hellwig1-7/+1
Move the ramfs aops to libfs and reuse them for kernfs and configfs. Thosw two did not wire up ->set_page_dirty before and now get __set_page_dirty_no_writeback, which is the right one for no-writeback address_space usage. Drop the now unused exports of the libfs helpers only used for ramfs-style pagecache usage. Link: https://lkml.kernel.org/r/20210614061512.3966143-3-hch@lst.de Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Reviewed-by: Jan Kara <jack@suse.cz> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-06-15kernfs: move revalidate to be near lookupIan Kent1-43/+43
While the dentry operation kernfs_dop_revalidate() is grouped with dentry type functions it also has a strong affinity to the inode operation ->lookup(). It makes sense to locate this function near to kernfs_iop_lookup() because we will be adding VFS negative dentry caching to reduce path lookup overhead for non-existent paths. There's no functional change from this patch. Signed-off-by: Ian Kent <raven@themaw.net> Reviewed-by: Miklos Szeredi <mszeredi@redhat.com> Link: https://lore.kernel.org/r/162375275365.232295.8995526416263659926.stgit@web.messagingengine.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-02-24Merge tag 'idmapped-mounts-v5.12' of ↵Linus Torvalds3-12/+22
git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux Pull idmapped mounts from Christian Brauner: "This introduces idmapped mounts which has been in the making for some time. Simply put, different mounts can expose the same file or directory with different ownership. This initial implementation comes with ports for fat, ext4 and with Christoph's port for xfs with more filesystems being actively worked on by independent people and maintainers. Idmapping mounts handle a wide range of long standing use-cases. Here are just a few: - Idmapped mounts make it possible to easily share files between multiple users or multiple machines especially in complex scenarios. For example, idmapped mounts will be used in the implementation of portable home directories in systemd-homed.service(8) where they allow users to move their home directory to an external storage device and use it on multiple computers where they are assigned different uids and gids. This effectively makes it possible to assign random uids and gids at login time. - It is possible to share files from the host with unprivileged containers without having to change ownership permanently through chown(2). - It is possible to idmap a container's rootfs and without having to mangle every file. For example, Chromebooks use it to share the user's Download folder with their unprivileged containers in their Linux subsystem. - It is possible to share files between containers with non-overlapping idmappings. - Filesystem that lack a proper concept of ownership such as fat can use idmapped mounts to implement discretionary access (DAC) permission checking. - They allow users to efficiently changing ownership on a per-mount basis without having to (recursively) chown(2) all files. In contrast to chown (2) changing ownership of large sets of files is instantenous with idmapped mounts. This is especially useful when ownership of a whole root filesystem of a virtual machine or container is changed. With idmapped mounts a single syscall mount_setattr syscall will be sufficient to change the ownership of all files. - Idmapped mounts always take the current ownership into account as idmappings specify what a given uid or gid is supposed to be mapped to. This contrasts with the chown(2) syscall which cannot by itself take the current ownership of the files it changes into account. It simply changes the ownership to the specified uid and gid. This is especially problematic when recursively chown(2)ing a large set of files which is commong with the aforementioned portable home directory and container and vm scenario. - Idmapped mounts allow to change ownership locally, restricting it to specific mounts, and temporarily as the ownership changes only apply as long as the mount exists. Several userspace projects have either already put up patches and pull-requests for this feature or will do so should you decide to pull this: - systemd: In a wide variety of scenarios but especially right away in their implementation of portable home directories. https://systemd.io/HOME_DIRECTORY/ - container runtimes: containerd, runC, LXD:To share data between host and unprivileged containers, unprivileged and privileged containers, etc. The pull request for idmapped mounts support in containerd, the default Kubernetes runtime is already up for quite a while now: https://github.com/containerd/containerd/pull/4734 - The virtio-fs developers and several users have expressed interest in using this feature with virtual machines once virtio-fs is ported. - ChromeOS: Sharing host-directories with unprivileged containers. I've tightly synced with all those projects and all of those listed here have also expressed their need/desire for this feature on the mailing list. For more info on how people use this there's a bunch of talks about this too. Here's just two recent ones: https://www.cncf.io/wp-content/uploads/2020/12/Rootless-Containers-in-Gitpod.pdf https://fosdem.org/2021/schedule/event/containers_idmap/ This comes with an extensive xfstests suite covering both ext4 and xfs: https://git.kernel.org/brauner/xfstests-dev/h/idmapped_mounts It covers truncation, creation, opening, xattrs, vfscaps, setid execution, setgid inheritance and more both with idmapped and non-idmapped mounts. It already helped to discover an unrelated xfs setgid inheritance bug which has since been fixed in mainline. It will be sent for inclusion with the xfstests project should you decide to merge this. In order to support per-mount idmappings vfsmounts are marked with user namespaces. The idmapping of the user namespace will be used to map the ids of vfs objects when they are accessed through that mount. By default all vfsmounts are marked with the initial user namespace. The initial user namespace is used to indicate that a mount is not idmapped. All operations behave as before and this is verified in the testsuite. Based on prior discussions we want to attach the whole user namespace and not just a dedicated idmapping struct. This allows us to reuse all the helpers that already exist for dealing with idmappings instead of introducing a whole new range of helpers. In addition, if we decide in the future that we are confident enough to enable unprivileged users to setup idmapped mounts the permission checking can take into account whether the caller is privileged in the user namespace the mount is currently marked with. The user namespace the mount will be marked with can be specified by passing a file descriptor refering to the user namespace as an argument to the new mount_setattr() syscall together with the new MOUNT_ATTR_IDMAP flag. The system call follows the openat2() pattern of extensibility. The following conditions must be met in order to create an idmapped mount: - The caller must currently have the CAP_SYS_ADMIN capability in the user namespace the underlying filesystem has been mounted in. - The underlying filesystem must support idmapped mounts. - The mount must not already be idmapped. This also implies that the idmapping of a mount cannot be altered once it has been idmapped. - The mount must be a detached/anonymous mount, i.e. it must have been created by calling open_tree() with the OPEN_TREE_CLONE flag and it must not already have been visible in the filesystem. The last two points guarantee easier semantics for userspace and the kernel and make the implementation significantly simpler. By default vfsmounts are marked with the initial user namespace and no behavioral or performance changes are observed. The manpage with a detailed description can be found here: https://git.kernel.org/brauner/man-pages/c/1d7b902e2875a1ff342e036a9f866a995640aea8 In order to support idmapped mounts, filesystems need to be changed and mark themselves with the FS_ALLOW_IDMAP flag in fs_flags. The patches to convert individual filesystem are not very large or complicated overall as can be seen from the included fat, ext4, and xfs ports. Patches for other filesystems are actively worked on and will be sent out separately. The xfstestsuite can be used to verify that port has been done correctly. The mount_setattr() syscall is motivated independent of the idmapped mounts patches and it's been around since July 2019. One of the most valuable features of the new mount api is the ability to perform mounts based on file descriptors only. Together with the lookup restrictions available in the openat2() RESOLVE_* flag namespace which we added in v5.6 this is the first time we are close to hardened and race-free (e.g. symlinks) mounting and path resolution. While userspace has started porting to the new mount api to mount proper filesystems and create new bind-mounts it is currently not possible to change mount options of an already existing bind mount in the new mount api since the mount_setattr() syscall is missing. With the addition of the mount_setattr() syscall we remove this last restriction and userspace can now fully port to the new mount api, covering every use-case the old mount api could. We also add the crucial ability to recursively change mount options for a whole mount tree, both removing and adding mount options at the same time. This syscall has been requested multiple times by various people and projects. There is a simple tool available at https://github.com/brauner/mount-idmapped that allows to create idmapped mounts so people can play with this patch series. I'll add support for the regular mount binary should you decide to pull this in the following weeks: Here's an example to a simple idmapped mount of another user's home directory: u1001@f2-vm:/$ sudo ./mount --idmap both:1000:1001:1 /home/ubuntu/ /mnt u1001@f2-vm:/$ ls -al /home/ubuntu/ total 28 drwxr-xr-x 2 ubuntu ubuntu 4096 Oct 28 22:07 . drwxr-xr-x 4 root root 4096 Oct 28 04:00 .. -rw------- 1 ubuntu ubuntu 3154 Oct 28 22:12 .bash_history -rw-r--r-- 1 ubuntu ubuntu 220 Feb 25 2020 .bash_logout -rw-r--r-- 1 ubuntu ubuntu 3771 Feb 25 2020 .bashrc -rw-r--r-- 1 ubuntu ubuntu 807 Feb 25 2020 .profile -rw-r--r-- 1 ubuntu ubuntu 0 Oct 16 16:11 .sudo_as_admin_successful -rw------- 1 ubuntu ubuntu 1144 Oct 28 00:43 .viminfo u1001@f2-vm:/$ ls -al /mnt/ total 28 drwxr-xr-x 2 u1001 u1001 4096 Oct 28 22:07 . drwxr-xr-x 29 root root 4096 Oct 28 22:01 .. -rw------- 1 u1001 u1001 3154 Oct 28 22:12 .bash_history -rw-r--r-- 1 u1001 u1001 220 Feb 25 2020 .bash_logout -rw-r--r-- 1 u1001 u1001 3771 Feb 25 2020 .bashrc -rw-r--r-- 1 u1001 u1001 807 Feb 25 2020 .profile -rw-r--r-- 1 u1001 u1001 0 Oct 16 16:11 .sudo_as_admin_successful -rw------- 1 u1001 u1001 1144 Oct 28 00:43 .viminfo u1001@f2-vm:/$ touch /mnt/my-file u1001@f2-vm:/$ setfacl -m u:1001:rwx /mnt/my-file u1001@f2-vm:/$ sudo setcap -n 1001 cap_net_raw+ep /mnt/my-file u1001@f2-vm:/$ ls -al /mnt/my-file -rw-rwxr--+ 1 u1001 u1001 0 Oct 28 22:14 /mnt/my-file u1001@f2-vm:/$ ls -al /home/ubuntu/my-file -rw-rwxr--+ 1 ubuntu ubuntu 0 Oct 28 22:14 /home/ubuntu/my-file u1001@f2-vm:/$ getfacl /mnt/my-file getfacl: Removing leading '/' from absolute path names # file: mnt/my-file # owner: u1001 # group: u1001 user::rw- user:u1001:rwx group::rw- mask::rwx other::r-- u1001@f2-vm:/$ getfacl /home/ubuntu/my-file getfacl: Removing leading '/' from absolute path names # file: home/ubuntu/my-file # owner: ubuntu # group: ubuntu user::rw- user:ubuntu:rwx group::rw- mask::rwx other::r--" * tag 'idmapped-mounts-v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux: (41 commits) xfs: remove the possibly unused mp variable in xfs_file_compat_ioctl xfs: support idmapped mounts ext4: support idmapped mounts fat: handle idmapped mounts tests: add mount_setattr() selftests fs: introduce MOUNT_ATTR_IDMAP fs: add mount_setattr() fs: add attr_flags_to_mnt_flags helper fs: split out functions to hold writers namespace: only take read lock in do_reconfigure_mnt() mount: make {lock,unlock}_mount_hash() static namespace: take lock_mount_hash() directly when changing flags nfs: do not export idmapped mounts overlayfs: do not mount on top of idmapped mounts ecryptfs: do not mount on top of idmapped mounts ima: handle idmapped mounts apparmor: handle idmapped mounts fs: make helpers idmap mount aware exec: handle idmapped mounts would_dump: handle idmapped mounts ...
2021-01-24fs: make helpers idmap mount awareChristian Brauner3-8/+16
Extend some inode methods with an additional user namespace argument. A filesystem that is aware of idmapped mounts will receive the user namespace the mount has been marked with. This can be used for additional permission checking and also to enable filesystems to translate between uids and gids if they need to. We have implemented all relevant helpers in earlier patches. As requested we simply extend the exisiting inode method instead of introducing new ones. This is a little more code churn but it's mostly mechanical and doesnt't leave us with additional inode methods. Link: https://lore.kernel.org/r/20210121131959.646623-25-christian.brauner@ubuntu.com Cc: Christoph Hellwig <hch@lst.de> Cc: David Howells <dhowells@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-24stat: handle idmapped mountsChristian Brauner1-1/+1
The generic_fillattr() helper fills in the basic attributes associated with an inode. Enable it to handle idmapped mounts. If the inode is accessed through an idmapped mount map it into the mount's user namespace before we store the uid and gid. If the initial user namespace is passed nothing changes so non-idmapped mounts will see identical behavior as before. Link: https://lore.kernel.org/r/20210121131959.646623-12-christian.brauner@ubuntu.com Cc: Christoph Hellwig <hch@lst.de> Cc: David Howells <dhowells@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: James Morris <jamorris@linux.microsoft.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-24acl: handle idmapped mountsChristian Brauner1-0/+2
The posix acl permission checking helpers determine whether a caller is privileged over an inode according to the acls associated with the inode. Add helpers that make it possible to handle acls on idmapped mounts. The vfs and the filesystems targeted by this first iteration make use of posix_acl_fix_xattr_from_user() and posix_acl_fix_xattr_to_user() to translate basic posix access and default permissions such as the ACL_USER and ACL_GROUP type according to the initial user namespace (or the superblock's user namespace) to and from the caller's current user namespace. Adapt these two helpers to handle idmapped mounts whereby we either map from or into the mount's user namespace depending on in which direction we're translating. Similarly, cap_convert_nscap() is used by the vfs to translate user namespace and non-user namespace aware filesystem capabilities from the superblock's user namespace to the caller's user namespace. Enable it to handle idmapped mounts by accounting for the mount's user namespace. In addition the fileystems targeted in the first iteration of this patch series make use of the posix_acl_chmod() and, posix_acl_update_mode() helpers. Both helpers perform permission checks on the target inode. Let them handle idmapped mounts. These two helpers are called when posix acls are set by the respective filesystems to handle this case we extend the ->set() method to take an additional user namespace argument to pass the mount's user namespace down. Link: https://lore.kernel.org/r/20210121131959.646623-9-christian.brauner@ubuntu.com Cc: Christoph Hellwig <hch@lst.de> Cc: David Howells <dhowells@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-24attr: handle idmapped mountsChristian Brauner1-2/+2
When file attributes are changed most filesystems rely on the setattr_prepare(), setattr_copy(), and notify_change() helpers for initialization and permission checking. Let them handle idmapped mounts. If the inode is accessed through an idmapped mount map it into the mount's user namespace. Afterwards the checks are identical to non-idmapped mounts. If the initial user namespace is passed nothing changes so non-idmapped mounts will see identical behavior as before. Helpers that perform checks on the ia_uid and ia_gid fields in struct iattr assume that ia_uid and ia_gid are intended values and have already been mapped correctly at the userspace-kernelspace boundary as we already do today. If the initial user namespace is passed nothing changes so non-idmapped mounts will see identical behavior as before. Link: https://lore.kernel.org/r/20210121131959.646623-8-christian.brauner@ubuntu.com Cc: Christoph Hellwig <hch@lst.de> Cc: David Howells <dhowells@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-24namei: make permission helpers idmapped mount awareChristian Brauner1-1/+1
The two helpers inode_permission() and generic_permission() are used by the vfs to perform basic permission checking by verifying that the caller is privileged over an inode. In order to handle idmapped mounts we extend the two helpers with an additional user namespace argument. On idmapped mounts the two helpers will make sure to map the inode according to the mount's user namespace and then peform identical permission checks to inode_permission() and generic_permission(). If the initial user namespace is passed nothing changes so non-idmapped mounts will see identical behavior as before. Link: https://lore.kernel.org/r/20210121131959.646623-6-christian.brauner@ubuntu.com Cc: Christoph Hellwig <hch@lst.de> Cc: David Howells <dhowells@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: James Morris <jamorris@linux.microsoft.com> Acked-by: Serge Hallyn <serge@hallyn.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-21kernfs: wire up ->splice_read and ->splice_writeChristoph Hellwig1-0/+2
Wire up the splice_read and splice_write methods to the default helpers using ->read_iter and ->write_iter now that those are implemented for kernfs. This restores support to use splice and sendfile on kernfs files. Fixes: 36e2c7421f02 ("fs: don't allow splice read/write without explicit ops") Reported-by: Siddharth Gupta <sidgup@codeaurora.org> Tested-by: Siddharth Gupta <sidgup@codeaurora.org> Signed-off-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20210120204631.274206-4-hch@lst.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-01-21kernfs: implement ->write_iterChristoph Hellwig1-18/+10
Switch kernfs to implement the write_iter method instead of plain old write to prepare to supporting splice and sendfile again. Signed-off-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20210120204631.274206-3-hch@lst.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-01-21kernfs: implement ->read_iterChristoph Hellwig1-23/+12
Switch kernfs to implement the read_iter method instead of plain old read to prepare to supporting splice and sendfile again. Signed-off-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20210120204631.274206-2-hch@lst.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-12-09fs/kernfs: remove the double check of dentry->inodeHui Su1-2/+1
In both kernfs_node_from_dentry() and in kernfs_dentry_node(), we will check the dentry->inode is NULL or not, which is superfluous. So remove the check in kernfs_node_from_dentry(). Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Hui Su <sh_def@163.com> Link: https://lore.kernel.org/r/20201113132143.GA119541@rlk Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-11-09kernfs: bring names in comments in line with codeWillem de Bruijn1-1/+1
Fix two stragglers in the comments of the below rename operation. Fixes: adc5e8b58f48 ("kernfs: drop s_ prefix from kernfs_node members") Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Willem de Bruijn <willemb@google.com> Link: https://lore.kernel.org/r/20201015185726.1386868-1-willemdebruijn.kernel@gmail.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-07-28fsnotify: pass dir and inode arguments to fsnotify()Amir Goldstein1-2/+3
The arguments of fsnotify() are overloaded and mean different things for different event types. Replace the to_tell argument with separate arguments @dir and @inode, because we may be sending to both dir and child. Using the @data argument to pass the child is not enough, because dirent events pass this argument (for audit), but we do not report to child. Document the new fsnotify() function argumenets. Link: https://lore.kernel.org/r/20200722125849.17418-7-amir73il@gmail.com Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
2020-07-28fsnotify: create helper fsnotify_inode()Amir Goldstein1-4/+2
Simple helper to consolidate biolerplate code. Link: https://lore.kernel.org/r/20200722125849.17418-5-amir73il@gmail.com Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
2020-07-27fsnotify: send event to parent and child with single callbackAmir Goldstein1-4/+6
Instead of calling fsnotify() twice, once with parent inode and once with child inode, if event should be sent to parent inode, send it with both parent and child inodes marks in object type iterator and call the backend handle_event() callback only once. The parent inode is assigned to the standard "inode" iterator type and the child inode is assigned to the special "child" iterator type. In that case, the bit FS_EVENT_ON_CHILD will be set in the event mask, the dir argument to handle_event will be the parent inode, the file_name argument to handle_event is non NULL and refers to the name of the child and the child inode can be accessed with fsnotify_data_inode(). This will allow fanotify to make decisions based on child or parent's ignored mask. For example, when a parent is interested in a specific event on its children, but a specific child wishes to ignore this event, the event will not be reported. This is not what happens with current code, but according to man page, it is the expected behavior. Link: https://lore.kernel.org/r/20200716084230.30611-15-amir73il@gmail.com Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
2020-07-15kernfs: do not call fsnotify() with name without a parentAmir Goldstein1-1/+1
When creating an FS_MODIFY event on inode itself (not on parent) the file_name argument should be NULL. The change to send a non NULL name to inode itself was done on purpuse as part of another commit, as Tejun writes: "...While at it, supply the target file name to fsnotify() from kernfs_node->name.". But this is wrong practice and inconsistent with inotify behavior when watching a single file. When a child is being watched (as opposed to the parent directory) the inotify event should contain the watch descriptor, but not the file name. Fixes: df6a58c5c5aa ("kernfs: don't depend on d_find_any_alias()...") Link: https://lore.kernel.org/r/20200708111156.24659-5-amir73il@gmail.com Acked-by: Tejun Heo <tj@kernel.org> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
2020-06-09mmap locking API: convert mmap_sem commentsMichel Lespinasse1-2/+2
Convert comments that reference mmap_sem to reference mmap_lock instead. [akpm@linux-foundation.org: fix up linux-next leftovers] [akpm@linux-foundation.org: s/lockaphore/lock/, per Vlastimil] [akpm@linux-foundation.org: more linux-next fixups, per Michel] Signed-off-by: Michel Lespinasse <walken@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com> Cc: Davidlohr Bueso <dbueso@suse.de> Cc: David Rientjes <rientjes@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Jerome Glisse <jglisse@redhat.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Laurent Dufour <ldufour@linux.ibm.com> Cc: Liam Howlett <Liam.Howlett@oracle.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ying Han <yinghan@google.com> Link: http://lkml.kernel.org/r/20200520052908.204642-13-walken@google.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-04-23kernfs: Change kernfs_node lockdep name to "kn->active"Waiman Long1-1/+1
The kernfs_node lockdep tracking is being done on kn->active, the active reference count. The other reference count (kn->count) is not tracked by lockdep. So change the lockdep name to reflect what it is tracking. Signed-off-by: Waiman Long <longman@redhat.com> Acked-by: Tejun Heo <tj@kernel.org> Link: https://lore.kernel.org/r/20200402171056.27871-1-longman@redhat.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-03-16kernfs: Add option to enable user xattrsDaniel Xu2-0/+91
User extended attributes are useful as metadata storage for kernfs consumers like cgroups. Especially in the case of cgroups, it is useful to have a central metadata store that multiple processes/services can use to coordinate actions. A concrete example is for userspace out of memory killers. We want to let delegated cgroup subtree owners (running as non-root) to be able to say "please avoid killing this cgroup". This is especially important for desktop linux as delegated subtrees owners are less likely to run as root. This patch introduces a new flag, KERNFS_ROOT_SUPPORT_USER_XATTR, that lets kernfs consumers enable user xattr support. An initial limit of 128 entries or 128KB -- whichever is hit first -- is placed per cgroup because xattrs come from kernel memory and we don't want to let unprivileged users accidentally eat up too much kernel memory. Signed-off-by: Daniel Xu <dxu@dxuuu.xyz> Acked-by: Chris Down <chris@chrisdown.name> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Tejun Heo <tj@kernel.org>
2020-03-16kernfs: Add removed_size out param for simple_xattr_setDaniel Xu1-1/+1
This helps set up size accounting in the next commit. Without this out param, it's difficult to find out the removed xattr size without taking a lock for longer and walking the xattr linked list twice. Signed-off-by: Daniel Xu <dxu@dxuuu.xyz> Acked-by: Chris Down <chris@chrisdown.name> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Tejun Heo <tj@kernel.org>
2020-02-05Merge branch 'imm.timestamp' of ↵Linus Torvalds1-3/+3
git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs Pull vfs timestamp updates from Al Viro: "More 64bit timestamp work" * 'imm.timestamp' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: kernfs: don't bother with timestamp truncation fs: Do not overload update_time fs: Delete timespec64_trunc() fs: ubifs: Eliminate timespec64_trunc() usage fs: ceph: Delete timespec64_trunc() usage fs: cifs: Delete usage of timespec64_trunc fs: fat: Eliminate timespec64_trunc() usage utimes: Clamp the timestamps in notify_change()
2020-01-14fs/kernfs/dir.c: Clean code by removing always true conditionMateusz Nosek1-1/+1
Previously there was an additional check if variable pos is not null. However, this check happens after entering while loop and only then, which can happen only if pos is not null. Therefore the additional check is redundant and can be removed. Signed-off-by: Mateusz Nosek <mateusznosek0@gmail.com> Acked-by: Tejun Heo <tj@kernel.org> Link: https://lore.kernel.org/r/20191230191628.21099-1-mateusznosek0@gmail.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-12-09kernfs: don't bother with timestamp truncationAl Viro1-3/+3
kernfs users are not going to have limited range or granularity anyway. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2019-12-06Merge branch 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfsLinus Torvalds1-1/+1
Pull vfs d_inode/d_flags memory ordering fixes from Al Viro: "Fallout from tree-wide audit for ->d_inode/->d_flags barriers use. Basically, the problem is that negative pinned dentries require careful treatment - unless ->d_lock is locked or parent is held at least shared, another thread can make them positive right under us. Most of the uses turned out to be safe - the main surprises as far as filesystems are concerned were - race in dget_parent() fastpath, that might end up with the caller observing the returned dentry _negative_, due to insufficient barriers. It is positive in memory, but we could end up seeing the wrong value of ->d_inode in CPU cache. Fixed. - manual checks that result of lookup_one_len_unlocked() is positive (and rejection of negatives). Again, insufficient barriers (we might end up with inconsistent observed values of ->d_inode and ->d_flags). Fixed by switching to a new primitive that does the checks itself and returns ERR_PTR(-ENOENT) instead of a negative dentry. That way we get rid of boilerplate converting negatives into ERR_PTR(-ENOENT) in the callers and have a single place to deal with the barrier-related mess - inside fs/namei.c rather than in every caller out there. The guts of pathname resolution *do* need to be careful - the race found by Ritesh is real, as well as several similar races. Fortunately, it turns out that we can take care of that with fairly local changes in there. The tree-wide audit had not been fun, and I hate the idea of repeating it. I think the right approach would be to annotate the places where we are _not_ guaranteed ->d_inode/->d_flags stability and have sparse catch regressions. But I'm still not sure what would be the least invasive way of doing that and it's clearly the next cycle fodder" * 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: fs/namei.c: fix missing barriers when checking positivity fix dget_parent() fastpath race new helper: lookup_positive_unlocked() fs/namei.c: pull positivity check into follow_managed()
2019-11-27Merge branch 'locking-core-for-linus' of ↵Linus Torvalds1-2/+2
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull locking updates from Ingo Molnar: "The main changes in this cycle were: - A comprehensive rewrite of the robust/PI futex code's exit handling to fix various exit races. (Thomas Gleixner et al) - Rework the generic REFCOUNT_FULL implementation using atomic_fetch_* operations so that the performance impact of the cmpxchg() loops is mitigated for common refcount operations. With these performance improvements the generic implementation of refcount_t should be good enough for everybody - and this got confirmed by performance testing, so remove ARCH_HAS_REFCOUNT and REFCOUNT_FULL entirely, leaving the generic implementation enabled unconditionally. (Will Deacon) - Other misc changes, fixes, cleanups" * 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (27 commits) lkdtm: Remove references to CONFIG_REFCOUNT_FULL locking/refcount: Remove unused 'refcount_error_report()' function locking/refcount: Consolidate implementations of refcount_t locking/refcount: Consolidate REFCOUNT_{MAX,SATURATED} definitions locking/refcount: Move saturation warnings out of line locking/refcount: Improve performance of generic REFCOUNT_FULL code locking/refcount: Move the bulk of the REFCOUNT_FULL implementation into the <linux/refcount.h> header locking/refcount: Remove unused refcount_*_checked() variants locking/refcount: Ensure integer operands are treated as signed locking/refcount: Define constants for saturation and max refcount values futex: Prevent exit livelock futex: Provide distinct return value when owner is exiting futex: Add mutex around futex exit futex: Provide state handling for exec() as well futex: Sanitize exit state handling futex: Mark the begin of futex exit explicitly futex: Set task::futex_state to DEAD right after handling futex exit futex: Split futex_mm_release() for exit/exec exit/exec: Seperate mm_release() futex: Replace PF_EXITPIDONE with a state ...
2019-11-15new helper: lookup_positive_unlocked()Al Viro1-1/+1
Most of the callers of lookup_one_len_unlocked() treat negatives are ERR_PTR(-ENOENT). Provide a helper that would do just that. Note that a pinned positive dentry remains positive - it's ->d_inode is stable, etc.; a pinned _negative_ dentry can become positive at any point as long as you are not holding its parent at least shared. So using lookup_one_len_unlocked() needs to be careful; lookup_positive_unlocked() is safer and that's what the callers end up open-coding anyway. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2019-11-12kernfs: use 64bit inos if ino_t is 64bitTejun Heo2-16/+33
Each kernfs_node is identified with a 64bit ID. The low 32bit is exposed as ino and the high gen. While this already allows using inos as keys by looking up with wildcard generation number of 0, it's adding unnecessary complications for 64bit ino archs which can directly use kernfs_node IDs as inos to uniquely identify each cgroup instance. This patch exposes IDs directly as inos on 64bit ino archs. The conversion is mostly straight-forward. * 32bit ino archs behave the same as before. 64bit ino archs now use the whole 64bit ID as ino and the generation number is fixed at 1. * 64bit inos still use the same idr allocator which gurantees that the lower 32bits identify the current live instance uniquely and the high 32bits are incremented whenever the low bits wrap. As the upper 32bits are no longer used as gen and we don't wanna start ino allocation with 33rd bit set, the initial value for highbits allocation is changed to 0 on 64bit ino archs. * blktrace exposes two 32bit numbers - (INO,GEN) pair - to identify the issuing cgroup. Userland builds FILEID_INO32_GEN fids from these numbers to look up the cgroups. To remain compatible with the behavior, always output (LOW32,HIGH32) which will be constructed back to the original 64bit ID by __kernfs_fh_to_dentry(). Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Namhyung Kim <namhyung@kernel.org>
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