linux-stable.git/include/linux/fs.h, branch v6.12.95

lsm: add backing_file LSM hooks

2026-07-04T11:43:31+00:00

[ Upstream commit 6af36aeb147a06dea47c49859cd6ca5659aeb987 ]

Stacked filesystems such as overlayfs do not currently provide the
necessary mechanisms for LSMs to properly enforce access controls on the
mmap() and mprotect() operations.  In order to resolve this gap, a LSM
security blob is being added to the backing_file struct and the following
new LSM hooks are being created:

 security_backing_file_alloc()
 security_backing_file_free()
 security_mmap_backing_file()

The first two hooks are to manage the lifecycle of the LSM security blob
in the backing_file struct, while the third provides a new mmap() access
control point for the underlying backing file.  It is also expected that
LSMs will likely want to update their security_file_mprotect() callback
to address issues with their mprotect() controls, but that does not
require a change to the security_file_mprotect() LSM hook.

There are a three other small changes to support these new LSM hooks:
* Pass the user file associated with a backing file down to
alloc_empty_backing_file() so it can be included in the
security_backing_file_alloc() hook.
* Add getter and setter functions for the backing_file struct LSM blob
as the backing_file struct remains private to fs/file_table.c.
* Constify the file struct field in the LSM common_audit_data struct to
better support LSMs that need to pass a const file struct pointer into
the common LSM audit code.

Thanks to Arnd Bergmann for identifying the missing EXPORT_SYMBOL_GPL()
and supplying a fixup.

Cc: stable@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-unionfs@vger.kernel.org
Cc: linux-erofs@lists.ozlabs.org
Reviewed-by: Amir Goldstein 
Reviewed-by: Serge Hallyn 
Reviewed-by: Christian Brauner 
Signed-off-by: Paul Moore 
[ Mainline declares lsm_backing_file_cache in security/lsm.h.  Linux 6.12.y
does not have security/lsm_init.c or security/lsm.h; the cache variable
is defined locally as static struct kmem_cache *lsm_backing_file_cache in
security/security.c. ]
Signed-off-by: Cai Xinchen 
Signed-off-by: Sasha Levin

fs: constify file ptr in backing_file accessor helpers

2026-07-04T11:43:31+00:00

[ Upstream commit 4e301d858af17ae2ce56886296e5458c5a08219a ]

Add internal helper backing_file_set_user_path() for the only
two cases that need to modify backing_file fields.

Signed-off-by: Amir Goldstein 
Link: https://lore.kernel.org/20250607115304.2521155-2-amir73il@gmail.com
Signed-off-by: Christian Brauner 
Signed-off-by: Cai Xinchen 
Signed-off-by: Sasha Levin

shmem: fix recovery on rename failures

2026-01-08T09:13:54+00:00

[ Upstream commit e1b4c6a58304fd490124cc2b454d80edc786665c ]

maple_tree insertions can fail if we are seriously short on memory;
simple_offset_rename() does not recover well if it runs into that.
The same goes for simple_offset_rename_exchange().

Moreover, shmem_whiteout() expects that if it succeeds, the caller will
progress to d_move(), i.e. that shmem_rename2() won't fail past the
successful call of shmem_whiteout().

Not hard to fix, fortunately - mtree_store() can't fail if the index we
are trying to store into is already present in the tree as a singleton.

For simple_offset_rename_exchange() that's enough - we just need to be
careful about the order of operations.

For simple_offset_rename() solution is to preinsert the target into the
tree for new_dir; the rest can be done without any potentially failing
operations.

That preinsertion has to be done in shmem_rename2() rather than in
simple_offset_rename() itself - otherwise we'd need to deal with the
possibility of failure after successful shmem_whiteout().

Fixes: a2e459555c5f ("shmem: stable directory offsets")
Reviewed-by: Christian Brauner 
Reviewed-by: Chuck Lever 
Signed-off-by: Al Viro 
Signed-off-by: Sasha Levin

ext4: introduce linear search for dentries

2025-09-19T14:35:42+00:00

[ Upstream commit 9e28059d56649a7212d5b3f8751ec021154ba3dd ]

This patch addresses an issue where some files in case-insensitive
directories become inaccessible due to changes in how the kernel
function, utf8_casefold(), generates case-folded strings from the
commit 5c26d2f1d3f5 ("unicode: Don't special case ignorable code
points").

There are good reasons why this change should be made; it's actually
quite stupid that Unicode seems to think that the characters ❤ and ❤️
should be casefolded.  Unfortimately because of the backwards
compatibility issue, this commit was reverted in 231825b2e1ff.

This problem is addressed by instituting a brute-force linear fallback
if a lookup fails on case-folded directory, which does result in a
performance hit when looking up files affected by the changing how
thekernel treats ignorable Uniode characters, or when attempting to
look up non-existent file names.  So this fallback can be disabled by
setting an encoding flag if in the future, the system administrator or
the manufacturer of a mobile handset or tablet can be sure that there
was no opportunity for a kernel to insert file names with incompatible
encodings.

Fixes: 5c26d2f1d3f5 ("unicode: Don't special case ignorable code points")
Signed-off-by: Theodore Ts'o 
Reviewed-by: Gabriel Krisman Bertazi 
Signed-off-by: Sasha Levin

fs: export anon_inode_make_secure_inode() and fix secretmem LSM bypass

2025-07-10T14:05:09+00:00

[ Upstream commit cbe4134ea4bc493239786220bd69cb8a13493190 ]

Export anon_inode_make_secure_inode() to allow KVM guest_memfd to create
anonymous inodes with proper security context. This replaces the current
pattern of calling alloc_anon_inode() followed by
inode_init_security_anon() for creating security context manually.

This change also fixes a security regression in secretmem where the
S_PRIVATE flag was not cleared after alloc_anon_inode(), causing
LSM/SELinux checks to be bypassed for secretmem file descriptors.

As guest_memfd currently resides in the KVM module, we need to export this
symbol for use outside the core kernel. In the future, guest_memfd might be
moved to core-mm, at which point the symbols no longer would have to be
exported. When/if that happens is still unclear.

Fixes: 2bfe15c52612 ("mm: create security context for memfd_secret inodes")
Suggested-by: David Hildenbrand 
Suggested-by: Mike Rapoport 
Signed-off-by: Shivank Garg 
Link: https://lore.kernel.org/20250620070328.803704-3-shivankg@amd.com
Acked-by: "Mike Rapoport (Microsoft)" 
Signed-off-by: Christian Brauner 
Signed-off-by: Sasha Levin

fuse: don't truncate cached, mutated symlink

2025-03-22T19:54:20+00:00

[ Upstream commit b4c173dfbb6c78568578ff18f9e8822d7bd0e31b ]

Fuse allows the value of a symlink to change and this property is exploited
by some filesystems (e.g. CVMFS).

It has been observed, that sometimes after changing the symlink contents,
the value is truncated to the old size.

This is caused by fuse_getattr() racing with fuse_reverse_inval_inode().
fuse_reverse_inval_inode() updates the fuse_inode's attr_version, which
results in fuse_change_attributes() exiting before updating the cached
attributes

This is okay, as the cached attributes remain invalid and the next call to
fuse_change_attributes() will likely update the inode with the correct
values.

The reason this causes problems is that cached symlinks will be
returned through page_get_link(), which truncates the symlink to
inode->i_size.  This is correct for filesystems that don't mutate
symlinks, but in this case it causes bad behavior.

The solution is to just remove this truncation.  This can cause a
regression in a filesystem that relies on supplying a symlink larger than
the file size, but this is unlikely.  If that happens we'd need to make
this behavior conditional.

Reported-by: Laura Promberger 
Tested-by: Sam Lewis 
Signed-off-by: Miklos Szeredi 
Link: https://lore.kernel.org/r/20250220100258.793363-1-mszeredi@redhat.com
Reviewed-by: Bernd Schubert 
Signed-off-by: Christian Brauner 
Signed-off-by: Sasha Levin

Revert "libfs: Add simple_offset_empty()"

2025-02-01T17:39:37+00:00

commit d7bde4f27ceef3dc6d72010a20d4da23db835a32 upstream.

simple_empty() and simple_offset_empty() perform the same task.
The latter's use as a canary to find bugs has not found any new
issues. A subsequent patch will remove the use of the mtree for
iterating directory contents, so revert back to using a similar
mechanism for determining whether a directory is indeed empty.

Only one such mechanism is ever needed.

Signed-off-by: Chuck Lever 
Link: https://lore.kernel.org/r/20241228175522.1854234-3-cel@kernel.org
Reviewed-by: Yang Erkun 
Signed-off-by: Christian Brauner 
Signed-off-by: Greg Kroah-Hartman

fs/block: Check for IOCB_DIRECT in generic_atomic_write_valid()

2024-12-05T13:01:11+00:00

[ Upstream commit c3be7ebbbce5201e151f17e28a6c807602f369c9 ]

Currently FMODE_CAN_ATOMIC_WRITE is set if the bdev can atomic write and
the file is open for direct IO. This does not work if the file is not
opened for direct IO, yet fcntl(O_DIRECT) is used on the fd later.

Change to check for direct IO on a per-IO basis in
generic_atomic_write_valid(). Since we want to report -EOPNOTSUPP for
non-direct IO for an atomic write, change to return an error code.

Relocate the block fops atomic write checks to the common write path, as to
catch non-direct IO.

Fixes: c34fc6f26ab8 ("fs: Initial atomic write support")
Reviewed-by: Christoph Hellwig 
Reviewed-by: Darrick J. Wong 
Signed-off-by: John Garry 
Link: https://lore.kernel.org/r/20241019125113.369994-3-john.g.garry@oracle.com
Signed-off-by: Jens Axboe 
Signed-off-by: Sasha Levin

block/fs: Pass an iocb to generic_atomic_write_valid()

2024-12-05T13:01:11+00:00

[ Upstream commit 9a8dbdadae509e5717ff6e5aa572ca0974d2101d ]

Darrick and Hannes both thought it better that generic_atomic_write_valid()
should be passed a struct iocb, and not just the member of that struct
which is referenced; see [0] and [1].

I think that makes a more generic and clean API, so make that change.

[0] https://lore.kernel.org/linux-block/680ce641-729b-4150-b875-531a98657682@suse.de/
[1] https://lore.kernel.org/linux-xfs/20240620212401.GA3058325@frogsfrogsfrogs/

Fixes: c34fc6f26ab8 ("fs: Initial atomic write support")
Suggested-by: Darrick J. Wong 
Suggested-by: Hannes Reinecke 
Reviewed-by: Darrick J. Wong 
Reviewed-by: Christoph Hellwig 
Signed-off-by: John Garry 
Link: https://lore.kernel.org/r/20241019125113.369994-2-john.g.garry@oracle.com
Signed-off-by: Jens Axboe 
Signed-off-by: Sasha Levin

bcachefs: do not use PF_MEMALLOC_NORECLAIM

2024-10-09T19:47:18+00:00

Patch series "remove PF_MEMALLOC_NORECLAIM" v3.


This patch (of 2):

bch2_new_inode relies on PF_MEMALLOC_NORECLAIM to try to allocate a new
inode to achieve GFP_NOWAIT semantic while holding locks. If this
allocation fails it will drop locks and use GFP_NOFS allocation context.

We would like to drop PF_MEMALLOC_NORECLAIM because it is really
dangerous to use if the caller doesn't control the full call chain with
this flag set. E.g. if any of the function down the chain needed
GFP_NOFAIL request the PF_MEMALLOC_NORECLAIM would override this and
cause unexpected failure.

While this is not the case in this particular case using the scoped gfp
semantic is not really needed bacause we can easily pus the allocation
context down the chain without too much clutter.

[akpm@linux-foundation.org: fix kerneldoc warnings]
Link: https://lkml.kernel.org/r/20240926172940.167084-1-mhocko@kernel.org
Link: https://lkml.kernel.org/r/20240926172940.167084-2-mhocko@kernel.org
Signed-off-by: Michal Hocko 
Reviewed-by: Christoph Hellwig 
Reviewed-by: Dave Chinner 
Reviewed-by: Jan Kara  # For vfs changes
Cc: Al Viro 
Cc: Christian Brauner 
Cc: James Morris 
Cc: Kent Overstreet 
Cc: Paul Moore 
Cc: Serge E. Hallyn 
Cc: Yafang Shao 
Cc: Matthew Wilcox (Oracle) 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton