kernel/linux.git/fs/fs_context.c, branch v6.12.80

fs: factor out vfs_parse_monolithic_sep() helper

2023-10-12T15:53:36+00:00

Factor out vfs_parse_monolithic_sep() from generic_parse_monolithic(), so filesystems could use it with a custom option separator callback. Acked-by: Christian Brauner Signed-off-by: Amir Goldstein

Merge tag 'v6.6-vfs.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2023-08-28T17:17:14+00:00

Pull misc vfs updates from Christian Brauner: "This contains the usual miscellaneous features, cleanups, and fixes for vfs and individual filesystems. Features: - Block mode changes on symlinks and rectify our broken semantics - Report file modifications via fsnotify() for splice - Allow specifying an explicit timeout for the "rootwait" kernel command line option. This allows to timeout and reboot instead of always waiting indefinitely for the root device to show up - Use synchronous fput for the close system call Cleanups: - Get rid of open-coded lockdep workarounds for async io submitters and replace it all with a single consolidated helper - Simplify epoll allocation helper - Convert simple_write_begin and simple_write_end to use a folio - Convert page_cache_pipe_buf_confirm() to use a folio - Simplify __range_close to avoid pointless locking - Disable per-cpu buffer head cache for isolated cpus - Port ecryptfs to kmap_local_page() api - Remove redundant initialization of pointer buf in pipe code - Unexport the d_genocide() function which is only used within core vfs - Replace printk(KERN_ERR) and WARN_ON() with WARN() Fixes: - Fix various kernel-doc issues - Fix refcount underflow for eventfds when used as EFD_SEMAPHORE - Fix a mainly theoretical issue in devpts - Check the return value of __getblk() in reiserfs - Fix a racy assert in i_readcount_dec - Fix integer conversion issues in various functions - Fix LSM security context handling during automounts that prevented NFS superblock sharing" * tag 'v6.6-vfs.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (39 commits) cachefiles: use kiocb_{start,end}_write() helpers ovl: use kiocb_{start,end}_write() helpers aio: use kiocb_{start,end}_write() helpers io_uring: use kiocb_{start,end}_write() helpers fs: create kiocb_{start,end}_write() helpers fs: add kerneldoc to file_{start,end}_write() helpers io_uring: rename kiocb_end_write() local helper splice: Convert page_cache_pipe_buf_confirm() to use a folio libfs: Convert simple_write_begin and simple_write_end to use a folio fs/dcache: Replace printk and WARN_ON by WARN fs/pipe: remove redundant initialization of pointer buf fs: Fix kernel-doc warnings devpts: Fix kernel-doc warnings doc: idmappings: fix an error and rephrase a paragraph init: Add support for rootwait timeout parameter vfs: fix up the assert in i_readcount_dec fs: Fix one kernel-doc comment docs: filesystems: idmappings: clarify from where idmappings are taken fs/buffer.c: disable per-CPU buffer_head cache for isolated CPUs vfs, security: Fix automount superblock LSM init problem, preventing NFS sb sharing ...

fs: Fix kernel-doc warnings

2023-08-19T10:12:12+00:00

These have a variety of causes and a corresponding variety of solutions. Signed-off-by: "Matthew Wilcox (Oracle)" Message-Id: <20230818200824.2720007-1-willy@infradead.org> Signed-off-by: Christian Brauner

vfs, security: Fix automount superblock LSM init problem, preventing NFS sb sharing

2023-08-15T06:32:30+00:00

When NFS superblocks are created by automounting, their LSM parameters aren't set in the fs_context struct prior to sget_fc() being called, leading to failure to match existing superblocks. This bug leads to messages like the following appearing in dmesg when fscache is enabled: NFS: Cache volume key already in use (nfs,4.2,2,108,106a8c0,1,,,,100000,100000,2ee,3a98,1d4c,3a98,1) Fix this by adding a new LSM hook to load fc->security for submount creation. Signed-off-by: David Howells Signed-off-by: Jeff Layton Link: https://lore.kernel.org/r/165962680944.3334508.6610023900349142034.stgit@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/165962729225.3357250.14350728846471527137.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/165970659095.2812394.6868894171102318796.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/166133579016.3678898.6283195019480567275.stgit@warthog.procyon.org.uk/ # v4 Link: https://lore.kernel.org/r/217595.1662033775@warthog.procyon.org.uk/ # v5 Fixes: 9bc61ab18b1d ("vfs: Introduce fs_context, switch vfs_kern_mount() to it.") Fixes: 779df6a5480f ("NFS: Ensure security label is set for root inode") Tested-by: Jeff Layton Acked-by: Casey Schaufler Acked-by: "Christian Brauner (Microsoft)" Acked-by: Paul Moore Reviewed-by: Jeff Layton Message-Id: <20230808-master-v9-1-e0ecde888221@kernel.org> Signed-off-by: Christian Brauner

fs: add FSCONFIG_CMD_CREATE_EXCL

2023-08-14T16:48:02+00:00

Summary ======= This introduces FSCONFIG_CMD_CREATE_EXCL which will allows userspace to implement something like mount -t ext4 --exclusive /dev/sda /B which fails if a superblock for the requested filesystem does already exist: Before this patch ----------------- $ sudo ./move-mount -f xfs -o source=/dev/sda4 /A Requesting filesystem type xfs Mount options requested: source=/dev/sda4 Attaching mount at /A Moving single attached mount Setting key(source) with val(/dev/sda4) $ sudo ./move-mount -f xfs -o source=/dev/sda4 /B Requesting filesystem type xfs Mount options requested: source=/dev/sda4 Attaching mount at /B Moving single attached mount Setting key(source) with val(/dev/sda4) After this patch with --exclusive as a switch for FSCONFIG_CMD_CREATE_EXCL -------------------------------------------------------------------------- $ sudo ./move-mount -f xfs --exclusive -o source=/dev/sda4 /A Requesting filesystem type xfs Request exclusive superblock creation Mount options requested: source=/dev/sda4 Attaching mount at /A Moving single attached mount Setting key(source) with val(/dev/sda4) $ sudo ./move-mount -f xfs --exclusive -o source=/dev/sda4 /B Requesting filesystem type xfs Request exclusive superblock creation Mount options requested: source=/dev/sda4 Attaching mount at /B Moving single attached mount Setting key(source) with val(/dev/sda4) Device or resource busy | move-mount.c: 300: do_fsconfig: i xfs: reusing existing filesystem not allowed Details ======= As mentioned on the list (cf. [1]-[3]) mount requests like mount -t ext4 /dev/sda /A are ambigous for userspace. Either a new superblock has been created and mounted or an existing superblock has been reused and a bind-mount has been created. This becomes clear in the following example where two processes create the same mount for the same block device: P1 P2 fd_fs = fsopen("ext4"); fd_fs = fsopen("ext4"); fsconfig(fd_fs, FSCONFIG_SET_STRING, "source", "/dev/sda"); fsconfig(fd_fs, FSCONFIG_SET_STRING, "source", "/dev/sda"); fsconfig(fd_fs, FSCONFIG_SET_STRING, "dax", "always"); fsconfig(fd_fs, FSCONFIG_SET_STRING, "resuid", "1000"); // wins and creates superblock fsconfig(fd_fs, FSCONFIG_CMD_CREATE, ...) // finds compatible superblock of P1 // spins until P1 sets SB_BORN and grabs a reference fsconfig(fd_fs, FSCONFIG_CMD_CREATE, ...) fd_mnt1 = fsmount(fd_fs); fd_mnt2 = fsmount(fd_fs); move_mount(fd_mnt1, "/A") move_mount(fd_mnt2, "/B") Not just does P2 get a bind-mount but the mount options that P2 requestes are silently ignored. The VFS itself doesn't, can't and shouldn't enforce filesystem specific mount option compatibility. It only enforces incompatibility for read-only <-> read-write transitions: mount -t ext4 /dev/sda /A mount -t ext4 -o ro /dev/sda /B The read-only request will fail with EBUSY as the VFS can't just silently transition a superblock from read-write to read-only or vica versa without risking security issues. To userspace this silent superblock reuse can become a security issue in because there is currently no straightforward way for userspace to know that they did indeed manage to create a new superblock and didn't just reuse an existing one. This adds a new FSCONFIG_CMD_CREATE_EXCL command to fsconfig() that returns EBUSY if an existing superblock would be reused. Userspace that needs to be sure that it did create a new superblock with the requested mount options can request superblock creation using this command. If the command succeeds they can be sure that they did create a new superblock with the requested mount options. This requires the new mount api. With the old mount api it would be necessary to plumb this through every legacy filesystem's file_system_type->mount() method. If they want this feature they are most welcome to switch to the new mount api. Following is an analysis of the effect of FSCONFIG_CMD_CREATE_EXCL on each high-level superblock creation helper: (1) get_tree_nodev() Always allocate new superblock. Hence, FSCONFIG_CMD_CREATE and FSCONFIG_CMD_CREATE_EXCL are equivalent. The binderfs or overlayfs filesystems are examples. (4) get_tree_keyed() Finds an existing superblock based on sb->s_fs_info. Hence, FSCONFIG_CMD_CREATE would reuse an existing superblock whereas FSCONFIG_CMD_CREATE_EXCL would reject it with EBUSY. The mqueue or nfsd filesystems are examples. (2) get_tree_bdev() This effectively works like get_tree_keyed(). The ext4 or xfs filesystems are examples. (3) get_tree_single() Only one superblock of this filesystem type can ever exist. Hence, FSCONFIG_CMD_CREATE would reuse an existing superblock whereas FSCONFIG_CMD_CREATE_EXCL would reject it with EBUSY. The securityfs or configfs filesystems are examples. Note that some single-instance filesystems never destroy the superblock once it has been created during the first mount. For example, if securityfs has been mounted at least onces then the created superblock will never be destroyed again as long as there is still an LSM making use it. Consequently, even if securityfs is unmounted and the superblock seemingly destroyed it really isn't which means that FSCONFIG_CMD_CREATE_EXCL will continue rejecting reusing an existing superblock. This is acceptable thugh since special purpose filesystems such as this shouldn't have a need to use FSCONFIG_CMD_CREATE_EXCL anyway and if they do it's probably to make sure that mount options aren't ignored. Following is an analysis of the effect of FSCONFIG_CMD_CREATE_EXCL on filesystems that make use of the low-level sget_fc() helper directly. They're all effectively variants on get_tree_keyed(), get_tree_bdev(), or get_tree_nodev(): (5) mtd_get_sb() Similar logic to get_tree_keyed(). (6) afs_get_tree() Similar logic to get_tree_keyed(). (7) ceph_get_tree() Similar logic to get_tree_keyed(). Already explicitly allows forcing the allocation of a new superblock via CEPH_OPT_NOSHARE. This turns it into get_tree_nodev(). (8) fuse_get_tree_submount() Similar logic to get_tree_nodev(). (9) fuse_get_tree() Forces reuse of existing FUSE superblock. Forces reuse of existing superblock if passed in file refers to an existing FUSE connection. If FSCONFIG_CMD_CREATE_EXCL is specified together with an fd referring to an existing FUSE connections this would cause the superblock reusal to fail. If reusing is the intent then FSCONFIG_CMD_CREATE_EXCL shouldn't be specified. (10) fuse_get_tree() -> get_tree_nodev() Same logic as in get_tree_nodev(). (11) fuse_get_tree() -> get_tree_bdev() Same logic as in get_tree_bdev(). (12) virtio_fs_get_tree() Same logic as get_tree_keyed(). (13) gfs2_meta_get_tree() Forces reuse of existing gfs2 superblock. Mounting gfs2meta enforces that a gf2s superblock must already exist. If not, it will error out. Consequently, mounting gfs2meta with FSCONFIG_CMD_CREATE_EXCL would always fail. If reusing is the intent then FSCONFIG_CMD_CREATE_EXCL shouldn't be specified. (14) kernfs_get_tree() Similar logic to get_tree_keyed(). (15) nfs_get_tree_common() Similar logic to get_tree_keyed(). Already explicitly allows forcing the allocation of a new superblock via NFS_MOUNT_UNSHARED. This effectively turns it into get_tree_nodev(). Link: [1] https://lore.kernel.org/linux-block/20230704-fasching-wertarbeit-7c6ffb01c83d@brauner Link: [2] https://lore.kernel.org/linux-block/20230705-pumpwerk-vielversprechend-a4b1fd947b65@brauner Link: [3] https://lore.kernel.org/linux-fsdevel/20230725-einnahmen-warnschilder-17779aec0a97@brauner Reviewed-by: Josef Bacik Reviewed-by: Christoph Hellwig Reviewed-by: Jan Kara Reviewed-by: Aleksa Sarai Message-Id: <20230802-vfs-super-exclusive-v2-4-95dc4e41b870@kernel.org> Signed-off-by: Christian Brauner

fs: avoid empty option when generating legacy mount string

2023-06-07T19:49:55+00:00

As each option string fragment is always prepended with a comma it would happen that the whole string always starts with a comma. This could be interpreted by filesystem drivers as an empty option and may produce errors. For example the NTFS driver from ntfs.ko behaves like this and fails when mounted via the new API. Link: https://github.com/util-linux/util-linux/issues/2298 Signed-off-by: Thomas Weißschuh Fixes: 3e1aeb00e6d1 ("vfs: Implement a filesystem superblock creation/configuration context") Cc: stable@vger.kernel.org Message-Id: <20230607-fs-empty-option-v1-1-20c8dbf4671b@weissschuh.net> Signed-off-by: Christian Brauner

vfs: fs_context: fix up param length parsing in legacy_parse_param

2022-01-18T07:23:19+00:00

The "PAGE_SIZE - 2 - size" calculation in legacy_parse_param() is an unsigned type so a large value of "size" results in a high positive value instead of a negative value as expected. Fix this by getting rid of the subtraction. Signed-off-by: Jamie Hill-Daniel Signed-off-by: William Liu Tested-by: Salvatore Bonaccorso Tested-by: Thadeu Lima de Souza Cascardo Acked-by: Dan Carpenter Acked-by: Al Viro Signed-off-by: Greg Kroah-Hartman Signed-off-by: Linus Torvalds

memcg: charge fs_context and legacy_fs_context

2021-09-03T16:58:12+00:00

This patch adds accounting flags to fs_context and legacy_fs_context allocation sites so that kernel could correctly charge these objects. We have written a PoC to demonstrate the effect of the missing-charging bugs. The PoC takes around 1,200MB unaccounted memory, while it is charged for only 362MB memory usage. We evaluate the PoC on QEMU x86_64 v5.2.90 + Linux kernel v5.10.19 + Debian buster. All the limitations including ulimits and sysctl variables are set as default. Specifically, the hard NOFILE limit and nr_open in sysctl are both 1,048,576. /*------------------------- POC code ----------------------------*/ #define _GNU_SOURCE #include #include #include #include #include #include #include #include #include #include #include #include #define errExit(msg) do { perror(msg); exit(EXIT_FAILURE); \ } while (0) #define STACK_SIZE (8 * 1024) #ifndef __NR_fsopen #define __NR_fsopen 430 #endif static inline int fsopen(const char *fs_name, unsigned int flags) { return syscall(__NR_fsopen, fs_name, flags); } static char thread_stack[512][STACK_SIZE]; int thread_fn(void* arg) { for (int i = 0; i< 800000; ++i) { int fsfd = fsopen("nfs", FSOPEN_CLOEXEC); if (fsfd == -1) { errExit("fsopen"); } } while(1); return 0; } int main(int argc, char *argv[]) { int thread_pid; for (int i = 0; i < 1; ++i) { thread_pid = clone(thread_fn, thread_stack[i] + STACK_SIZE, \ SIGCHLD, NULL); } while(1); return 0; } /*-------------------------- end --------------------------------*/ Link: https://lkml.kernel.org/r/1626517201-24086-1-git-send-email-nglaive@gmail.com Signed-off-by: Yutian Yang Reviewed-by: Shakeel Butt Cc: Michal Hocko Cc: Johannes Weiner Cc: Vladimir Davydov Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

fs: add vfs_parse_fs_param_source() helper

2021-07-14T16:19:06+00:00

Add a simple helper that filesystems can use in their parameter parser to parse the "source" parameter. A few places open-coded this function and that already caused a bug in the cgroup v1 parser that we fixed. Let's make it harder to get this wrong by introducing a helper which performs all necessary checks. Link: https://syzkaller.appspot.com/bug?id=6312526aba5beae046fdae8f00399f87aab48b12 Cc: Christoph Hellwig Cc: Alexander Viro Cc: Dmitry Vyukov Signed-off-by: Christian Brauner Signed-off-by: Linus Torvalds

treewide: Use fallthrough pseudo-keyword

2020-08-23T22:36:59+00:00

Replace the existing /* fall through */ comments and its variants with the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary fall-through markings when it is the case. [1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through Signed-off-by: Gustavo A. R. Silva