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

fcntl: make F_DUPFD_QUERY associative

2024-12-05T13:02:47+00:00

commit 2714b0d1f36999dbd99a3474a24e7301acbd74f1 upstream. Currently when passing a closed file descriptor to fcntl(fd, F_DUPFD_QUERY, fd_dup) the order matters: fd = open("/dev/null"); fd_dup = dup(fd); When we now close one of the file descriptors we get: (1) fcntl(fd, fd_dup) // -EBADF (2) fcntl(fd_dup, fd) // 0 aka not equal depending on which file descriptor is passed first. That's not a huge deal but it gives the api I slightly weird feel. Make it so that the order doesn't matter by requiring that both file descriptors are valid: (1') fcntl(fd, fd_dup) // -EBADF (2') fcntl(fd_dup, fd) // -EBADF Link: https://lore.kernel.org/r/20241008-duften-formel-251f967602d5@brauner Fixes: c62b758bae6a ("fcntl: add F_DUPFD_QUERY fcntl()") Reviewed-by: Jeff Layton Reviewed-By: Lennart Poettering Cc: stable@vger.kernel.org Reported-by: Lennart Poettering Signed-off-by: Christian Brauner Signed-off-by: Greg Kroah-Hartman

Merge tag 'pull-stable-struct_fd' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2024-09-23T16:35:36+00:00

Pull 'struct fd' updates from Al Viro: "Just the 'struct fd' layout change, with conversion to accessor helpers" * tag 'pull-stable-struct_fd' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: add struct fd constructors, get rid of __to_fd() struct fd: representation change introduce fd_file(), convert all accessors to it.

Merge tag 'lsm-pr-20240911' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm

2024-09-16T16:19:47+00:00

Pull lsm updates from Paul Moore: - Move the LSM framework to static calls This transitions the vast majority of the LSM callbacks into static calls. Those callbacks which haven't been converted were left as-is due to the general ugliness of the changes required to support the static call conversion; we can revisit those callbacks at a future date. - Add the Integrity Policy Enforcement (IPE) LSM This adds a new LSM, Integrity Policy Enforcement (IPE). There is plenty of documentation about IPE in this patches, so I'll refrain from going into too much detail here, but the basic motivation behind IPE is to provide a mechanism such that administrators can restrict execution to only those binaries which come from integrity protected storage, e.g. a dm-verity protected filesystem. You will notice that IPE requires additional LSM hooks in the initramfs, dm-verity, and fs-verity code, with the associated patches carrying ACK/review tags from the associated maintainers. We couldn't find an obvious maintainer for the initramfs code, but the IPE patchset has been widely posted over several years. Both Deven Bowers and Fan Wu have contributed to IPE's development over the past several years, with Fan Wu agreeing to serve as the IPE maintainer moving forward. Once IPE is accepted into your tree, I'll start working with Fan to ensure he has the necessary accounts, keys, etc. so that he can start submitting IPE pull requests to you directly during the next merge window. - Move the lifecycle management of the LSM blobs to the LSM framework Management of the LSM blobs (the LSM state buffers attached to various kernel structs, typically via a void pointer named "security" or similar) has been mixed, some blobs were allocated/managed by individual LSMs, others were managed by the LSM framework itself. Starting with this pull we move management of all the LSM blobs, minus the XFRM blob, into the framework itself, improving consistency across LSMs, and reducing the amount of duplicated code across LSMs. Due to some additional work required to migrate the XFRM blob, it has been left as a todo item for a later date; from a practical standpoint this omission should have little impact as only SELinux provides a XFRM LSM implementation. - Fix problems with the LSM's handling of F_SETOWN The LSM hook for the fcntl(F_SETOWN) operation had a couple of problems: it was racy with itself, and it was disconnected from the associated DAC related logic in such a way that the LSM state could be updated in cases where the DAC state would not. We fix both of these problems by moving the security_file_set_fowner() hook into the same section of code where the DAC attributes are updated. Not only does this resolve the DAC/LSM synchronization issue, but as that code block is protected by a lock, it also resolve the race condition. - Fix potential problems with the security_inode_free() LSM hook Due to use of RCU to protect inodes and the placement of the LSM hook associated with freeing the inode, there is a bit of a challenge when it comes to managing any LSM state associated with an inode. The VFS folks are not open to relocating the LSM hook so we have to get creative when it comes to releasing an inode's LSM state. Traditionally we have used a single LSM callback within the hook that is triggered when the inode is "marked for death", but not actually released due to RCU. Unfortunately, this causes problems for LSMs which want to take an action when the inode's associated LSM state is actually released; so we add an additional LSM callback, inode_free_security_rcu(), that is called when the inode's LSM state is released in the RCU free callback. - Refactor two LSM hooks to better fit the LSM return value patterns The vast majority of the LSM hooks follow the "return 0 on success, negative values on failure" pattern, however, there are a small handful that have unique return value behaviors which has caused confusion in the past and makes it difficult for the BPF verifier to properly vet BPF LSM programs. This includes patches to convert two of these"special" LSM hooks to the common 0/-ERRNO pattern. - Various cleanups and improvements A handful of patches to remove redundant code, better leverage the IS_ERR_OR_NULL() helper, add missing "static" markings, and do some minor style fixups. * tag 'lsm-pr-20240911' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm: (40 commits) security: Update file_set_fowner documentation fs: Fix file_set_fowner LSM hook inconsistencies lsm: Use IS_ERR_OR_NULL() helper function lsm: remove LSM_COUNT and LSM_CONFIG_COUNT ipe: Remove duplicated include in ipe.c lsm: replace indirect LSM hook calls with static calls lsm: count the LSMs enabled at compile time kernel: Add helper macros for loop unrolling init/main.c: Initialize early LSMs after arch code, static keys and calls. MAINTAINERS: add IPE entry with Fan Wu as maintainer documentation: add IPE documentation ipe: kunit test for parser scripts: add boot policy generation program ipe: enable support for fs-verity as a trust provider fsverity: expose verified fsverity built-in signatures to LSMs lsm: add security_inode_setintegrity() hook ipe: add support for dm-verity as a trust provider dm-verity: expose root hash digest and signature data to LSMs block,lsm: add LSM blob and new LSM hooks for block devices ipe: add permissive toggle ...

Merge tag 'vfs-6.12.file' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2024-09-16T07:14:02+00:00

Pull vfs file updates from Christian Brauner: "This is the work to cleanup and shrink struct file significantly. Right now, (focusing on x86) struct file is 232 bytes. After this series struct file will be 184 bytes aka 3 cacheline and a spare 8 bytes for future extensions at the end of the struct. With struct file being as ubiquitous as it is this should make a difference for file heavy workloads and allow further optimizations in the future. - struct fown_struct was embedded into struct file letting it take up 32 bytes in total when really it shouldn't even be embedded in struct file in the first place. Instead, actual users of struct fown_struct now allocate the struct on demand. This frees up 24 bytes. - Move struct file_ra_state into the union containg the cleanup hooks and move f_iocb_flags out of the union. This closes a 4 byte hole we created earlier and brings struct file to 192 bytes. Which means struct file is 3 cachelines and we managed to shrink it by 40 bytes. - Reorder struct file so that nothing crosses a cacheline. I suspect that in the future we will end up reordering some members to mitigate false sharing issues or just because someone does actually provide really good perf data. - Shrinking struct file to 192 bytes is only part of the work. Files use a slab that is SLAB_TYPESAFE_BY_RCU and when a kmem cache is created with SLAB_TYPESAFE_BY_RCU the free pointer must be located outside of the object because the cache doesn't know what part of the memory can safely be overwritten as it may be needed to prevent object recycling. That has the consequence that SLAB_TYPESAFE_BY_RCU may end up adding a new cacheline. So this also contains work to add a new kmem_cache_create_rcu() function that allows the caller to specify an offset where the freelist pointer is supposed to be placed. Thus avoiding the implicit addition of a fourth cacheline. - And finally this removes the f_version member in struct file. The f_version member isn't particularly well-defined. It is mainly used as a cookie to detect concurrent seeks when iterating directories. But it is also abused by some subsystems for completely unrelated things. It is mostly a directory and filesystem specific thing that doesn't really need to live in struct file and with its wonky semantics it really lacks a specific function. For pipes, f_version is (ab)used to defer poll notifications until a write has happened. And struct pipe_inode_info is used by multiple struct files in their ->private_data so there's no chance of pushing that down into file->private_data without introducing another pointer indirection. But pipes don't rely on f_pos_lock so this adds a union into struct file encompassing f_pos_lock and a pipe specific f_pipe member that pipes can use. This union of course can be extended to other file types and is similar to what we do in struct inode already" * tag 'vfs-6.12.file' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (26 commits) fs: remove f_version pipe: use f_pipe fs: add f_pipe ubifs: store cookie in private data ufs: store cookie in private data udf: store cookie in private data proc: store cookie in private data ocfs2: store cookie in private data input: remove f_version abuse ext4: store cookie in private data ext2: store cookie in private data affs: store cookie in private data fs: add generic_llseek_cookie() fs: use must_set_pos() fs: add must_set_pos() fs: add vfs_setpos_cookie() s390: remove unused f_version ceph: remove unused f_version adi: remove unused f_version mm: Removed @freeptr_offset to prevent doc warning ...

fs: Fix file_set_fowner LSM hook inconsistencies

2024-09-09T16:30:51+00:00

The fcntl's F_SETOWN command sets the process that handle SIGIO/SIGURG for the related file descriptor. Before this change, the file_set_fowner LSM hook was always called, ignoring the VFS logic which may not actually change the process that handles SIGIO (e.g. TUN, TTY, dnotify), nor update the related UID/EUID. Moreover, because security_file_set_fowner() was called without lock (e.g. f_owner.lock), concurrent F_SETOWN commands could result to a race condition and inconsistent LSM states (e.g. SELinux's fown_sid) compared to struct fown_struct's UID/EUID. This change makes sure the LSM states are always in sync with the VFS state by moving the security_file_set_fowner() call close to the UID/EUID updates and using the same f_owner.lock . Rename f_modown() to __f_setown() to simplify code. Cc: stable@vger.kernel.org Cc: Al Viro Cc: Casey Schaufler Cc: Christian Brauner Cc: James Morris Cc: Jann Horn Cc: Ondrej Mosnacek Cc: Paul Moore Cc: Serge E. Hallyn Cc: Stephen Smalley Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Mickaël Salaün Signed-off-by: Paul Moore

file: reclaim 24 bytes from f_owner

2024-08-28T11:05:39+00:00

We do embedd struct fown_struct into struct file letting it take up 32 bytes in total. We could tweak struct fown_struct to be more compact but really it shouldn't even be embedded in struct file in the first place. Instead, actual users of struct fown_struct should allocate the struct on demand. This frees up 24 bytes in struct file. That will have some potentially user-visible changes for the ownership fcntl()s. Some of them can now fail due to allocation failures. Practically, that probably will almost never happen as the allocations are small and they only happen once per file. The fown_struct is used during kill_fasync() which is used by e.g., pipes to generate a SIGIO signal. Sending of such signals is conditional on userspace having set an owner for the file using one of the F_OWNER fcntl()s. Such users will be unaffected if struct fown_struct is allocated during the fcntl() call. There are a few subsystems that call __f_setown() expecting file->f_owner to be allocated: (1) tun devices file->f_op->fasync::tun_chr_fasync() -> __f_setown() There are no callers of tun_chr_fasync(). (2) tty devices file->f_op->fasync::tty_fasync() -> __tty_fasync() -> __f_setown() tty_fasync() has no additional callers but __tty_fasync() has. Note that __tty_fasync() only calls __f_setown() if the @on argument is true. It's called from: file->f_op->release::tty_release() -> tty_release() -> __tty_fasync() -> __f_setown() tty_release() calls __tty_fasync() with @on false => __f_setown() is never called from tty_release(). => All callers of tty_release() are safe as well. file->f_op->release::tty_open() -> tty_release() -> __tty_fasync() -> __f_setown() __tty_hangup() calls __tty_fasync() with @on false => __f_setown() is never called from tty_release(). => All callers of __tty_hangup() are safe as well. From the callchains it's obvious that (1) and (2) end up getting called via file->f_op->fasync(). That can happen either through the F_SETFL fcntl() with the FASYNC flag raised or via the FIOASYNC ioctl(). If FASYNC is requested and the file isn't already FASYNC then file->f_op->fasync() is called with @on true which ends up causing both (1) and (2) to call __f_setown(). (1) and (2) are the only subsystems that call __f_setown() from the file->f_op->fasync() handler. So both (1) and (2) have been updated to allocate a struct fown_struct prior to calling fasync_helper() to register with the fasync infrastructure. That's safe as they both call fasync_helper() which also does allocations if @on is true. The other interesting case are file leases: (3) file leases lease_manager_ops->lm_setup::lease_setup() -> __f_setown() Which in turn is called from: generic_add_lease() -> lease_manager_ops->lm_setup::lease_setup() -> __f_setown() So here again we can simply make generic_add_lease() allocate struct fown_struct prior to the lease_manager_ops->lm_setup::lease_setup() which happens under a spinlock. With that the two remaining subsystems that call __f_setown() are: (4) dnotify (5) sockets Both have their own custom ioctls to set struct fown_struct and both have been converted to allocate a struct fown_struct on demand from their respective ioctls. Interactions with O_PATH are fine as well e.g., when opening a /dev/tty as O_PATH then no file->f_op->open() happens thus no file->f_owner is allocated. That's fine as no file operation will be set for those and the device has never been opened. fcntl()s called on such things will just allocate a ->f_owner on demand. Although I have zero idea why'd you care about f_owner on an O_PATH fd. Link: https://lore.kernel.org/r/20240813-work-f_owner-v2-1-4e9343a79f9f@kernel.org Reviewed-by: Jeff Layton Signed-off-by: Christian Brauner

fcntl: add F_CREATED_QUERY

2024-08-19T11:44:34+00:00

Systemd has a helper called openat_report_new() that returns whether a file was created anew or it already existed before for cases where O_CREAT has to be used without O_EXCL (cf. [1]). That apparently isn't something that's specific to systemd but it's where I noticed it. The current logic is that it first attempts to open the file without O_CREAT | O_EXCL and if it gets ENOENT the helper tries again with both flags. If that succeeds all is well. If it now reports EEXIST it retries. That works fairly well but some corner cases make this more involved. If this operates on a dangling symlink the first openat() without O_CREAT | O_EXCL will return ENOENT but the second openat() with O_CREAT | O_EXCL will fail with EEXIST. The reason is that openat() without O_CREAT | O_EXCL follows the symlink while O_CREAT | O_EXCL doesn't for security reasons. So it's not something we can really change unless we add an explicit opt-in via O_FOLLOW which seems really ugly. The caller could try and use fanotify() to register to listen for creation events in the directory before calling openat(). The caller could then compare the returned tid to its own tid to ensure that even in threaded environments it actually created the file. That might work but is a lot of work for something that should be fairly simple and I'm uncertain about it's reliability. The caller could use a bpf lsm hook to hook into security_file_open() to figure out whether they created the file. That also seems a bit wild. So let's add F_CREATED_QUERY which allows the caller to check whether they actually did create the file. That has caveats of course but I don't think they are problematic: * In multi-threaded environments a thread can only be sure that it did create the file if it calls openat() with O_CREAT. In other words, it's obviously not enough to just go through it's fdtable and check these fds because another thread could've created the file. * If there's any codepaths where an openat() with O_CREAT would yield the same struct file as that of another thread it would obviously cause wrong results. I'm not aware of any such codepaths from openat() itself. Imho, that would be a bug. * Related to the previous point, calling the new fcntl() on files created and opened via special-purpose system calls or ioctl()s would cause wrong results only if the affected subsystem a) raises FMODE_CREATED and b) may return the same struct file for two different calls. I'm not seeing anything outside of regular VFS code that raises FMODE_CREATED. There is code for b) in e.g., the drm layer where the same struct file is resurfaced but again FMODE_CREATED isn't used and it would be very misleading if it did. Link: https://github.com/systemd/systemd/blob/11d5e2b5fbf9f6bfa5763fd45b56829ad4f0777f/src/basic/fs-util.c#L1078 [1] Link: https://lore.kernel.org/r/20240724-work-fcntl-v1-1-e8153a2f1991@kernel.org Reviewed-by: Jeff Layton Reviewed-by: Jan Kara Signed-off-by: Christian Brauner

introduce fd_file(), convert all accessors to it.

2024-08-13T02:00:43+00:00

For any changes of struct fd representation we need to turn existing accesses to fields into calls of wrappers. Accesses to struct fd::flags are very few (3 in linux/file.h, 1 in net/socket.c, 3 in fs/overlayfs/file.c and 3 more in explicit initializers). Those can be dealt with in the commit converting to new layout; accesses to struct fd::file are too many for that. This commit converts (almost) all of f.file to fd_file(f). It's not entirely mechanical ('file' is used as a member name more than just in struct fd) and it does not even attempt to distinguish the uses in pointer context from those in boolean context; the latter will be eventually turned into a separate helper (fd_empty()). NOTE: mass conversion to fd_empty(), tempting as it might be, is a bad idea; better do that piecewise in commit that convert from fdget...() to CLASS(...). [conflicts in fs/fhandle.c, kernel/bpf/syscall.c, mm/memcontrol.c caught by git; fs/stat.c one got caught by git grep] [fs/xattr.c conflict] Reviewed-by: Christian Brauner Signed-off-by: Al Viro

fcntl: add F_DUPFD_QUERY fcntl()

2024-05-10T06:26:31+00:00

Often userspace needs to know whether two file descriptors refer to the same struct file. For example, systemd uses this to filter out duplicate file descriptors in it's file descriptor store (cf. [1]) and vulkan uses it to compare dma-buf fds (cf. [2]). The only api we provided for this was kcmp() but that's not generally available or might be disallowed because it is way more powerful (allows ordering of file pointers, operates on non-current task) etc. So give userspace a simple way of comparing two file descriptors for sameness adding a new fcntl() F_DUDFD_QUERY. Link: https://github.com/systemd/systemd/blob/a4f0e0da3573a10bc5404142be8799418760b1d1/src/basic/fd-util.c#L517 [1] Link: https://gitlab.freedesktop.org/wlroots/wlroots/-/blob/master/render/vulkan/texture.c#L490 [2] Signed-off-by: Linus Torvalds [brauner: commit message] Signed-off-by: Christian Brauner

Merge tag 'vfs-6.9.iomap' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2024-03-11T17:07:03+00:00

Pull iomap updates from Christian Brauner: - Restore read-write hints in struct bio through the bi_write_hint member for the sake of UFS devices in mobile applications. This can result in up to 40% lower write amplification in UFS devices. The patch series that builds on this will be coming in via the SCSI maintainers (Bart) - Overhaul the iomap writeback code. Afterwards ->map_blocks() is able to map multiple blocks at once as long as they're in the same folio. This reduces CPU usage for buffered write workloads on e.g., xfs on systems with lots of cores (Christoph) - Record processed bytes in iomap_iter() trace event (Kassey) - Extend iomap_writepage_map() trace event after Christoph's ->map_block() changes to map mutliple blocks at once (Zhang) * tag 'vfs-6.9.iomap' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (22 commits) iomap: Add processed for iomap_iter iomap: add pos and dirty_len into trace_iomap_writepage_map block, fs: Restore the per-bio/request data lifetime fields fs: Propagate write hints to the struct block_device inode fs: Move enum rw_hint into a new header file fs: Split fcntl_rw_hint() fs: Verify write lifetime constants at compile time fs: Fix rw_hint validation iomap: pass the length of the dirty region to ->map_blocks iomap: map multiple blocks at a time iomap: submit ioends immediately iomap: factor out a iomap_writepage_map_block helper iomap: only call mapping_set_error once for each failed bio iomap: don't chain bios iomap: move the iomap_sector sector calculation out of iomap_add_to_ioend iomap: clean up the iomap_alloc_ioend calling convention iomap: move all remaining per-folio logic into iomap_writepage_map iomap: factor out a iomap_writepage_handle_eof helper iomap: move the PF_MEMALLOC check to iomap_writepages iomap: move the io_folios field out of struct iomap_ioend ...