Merge branch 'next' into for-linus

Prepare input updates for 6.12 merge window.

Merge remote-tracking branch 'vfs/stable-struct_fd'

Merge Al Viro's struct fd refactorings.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

Merge tag 'v6.10' into next

Sync up with mainline to bring in device_for_each_child_node_scoped()
and other newer APIs.

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

Pull 'struct fd' updates from Al Viro:
"Just the 'struct fd' layout change, with conversion to accessor

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

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.

show more ...

introduce fd_file(), convert all accessors to it.

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 ve

introduce fd_file(), convert all accessors to it.

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 <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

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Merge branch 'slab/for-6.12/kmem_cache_args' into slab/for-next

Merge kmem_cache_create() refactoring by Christian Brauner.

Note this includes a merge of the vfs.file tree that contains the
prerequ

Merge branch 'slab/for-6.12/kmem_cache_args' into slab/for-next

Merge kmem_cache_create() refactoring by Christian Brauner.

Note this includes a merge of the vfs.file tree that contains the
prerequisity kmem_cache_create_rcu() work.

show more ...

Merge branch 'vfs.file' of gitolite.kernel.org:pub/scm/linux/kernel/git/vfs/vfs into slab/for-6.12/kmem_cache_args

Merge prerequisities from the vfs git tree for the following series that
introduces

Merge branch 'vfs.file' of gitolite.kernel.org:pub/scm/linux/kernel/git/vfs/vfs into slab/for-6.12/kmem_cache_args

Merge prerequisities from the vfs git tree for the following series that
introduces kmem_cache_args. The vfs.file branch includes the addition of
kmem_cache_create_rcu() which was needed in vfs for the filp cache
optimization. The following series refactors this code.

show more ...

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

Pull lsm updates from Paul Moore:

- Move the LSM framework to static calls

This transitions the vast ma

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

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
...

show more ...

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

Pull vfs file updates from Christian Brauner:
"This is the work to cleanup and shrink struct file significantly.

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

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
...

show more ...

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

Pull misc vfs updates from Christian Brauner:
"This contains the usual pile of misc updates:

Features:

- Add

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

Pull misc vfs updates from Christian Brauner:
"This contains the usual pile of misc updates:

Features:

- Add F_CREATED_QUERY fcntl() that allows userspace to query whether
a file was actually created. Often userspace wants to know whether
an O_CREATE request did actually create a file without using
O_EXCL. The current logic is that to first attempts to open the
file without O_CREAT | O_EXCL and if ENOENT is returned userspace
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.

All available workarounds are really nasty (fanotify, bpf lsm etc)
so add a simple fcntl().

- Try an opportunistic lookup for O_CREAT. Today, when opening a file
we'll typically do a fast lookup, but if O_CREAT is set, the kernel
always takes the exclusive inode lock. This was likely done with
the expectation that O_CREAT means that we always expect to do the
create, but that's often not the case. Many programs set O_CREAT
even in scenarios where the file already exists (see related
F_CREATED_QUERY patch motivation above).

The series contained in the pr rearranges the pathwalk-for-open
code to also attempt a fast_lookup in certain O_CREAT cases. If a
positive dentry is found, the inode_lock can be avoided altogether
and it can stay in rcuwalk mode for the last step_into.

- Expose the 64 bit mount id via name_to_handle_at()

Now that we provide a unique 64-bit mount ID interface in statx(2),
we can now provide a race-free way for name_to_handle_at(2) to
provide a file handle and corresponding mount without needing to
worry about racing with /proc/mountinfo parsing or having to open a
file just to do statx(2).

While this is not necessary if you are using AT_EMPTY_PATH and
don't care about an extra statx(2) call, users that pass full paths
into name_to_handle_at(2) need to know which mount the file handle
comes from (to make sure they don't try to open_by_handle_at a file
handle from a different filesystem) and switching to AT_EMPTY_PATH
would require allocating a file for every name_to_handle_at(2) call

- Add a per dentry expire timeout to autofs

There are two fairly well known automounter map formats, the autofs
format and the amd format (more or less System V and Berkley).

Some time ago Linux autofs added an amd map format parser that
implemented a fair amount of the amd functionality. This was done
within the autofs infrastructure and some functionality wasn't
implemented because it either didn't make sense or required extra
kernel changes. The idea was to restrict changes to be within the
existing autofs functionality as much as possible and leave changes
with a wider scope to be considered later.

One of these changes is implementing the amd options:
1) "unmount", expire this mount according to a timeout (same as
the current autofs default).
2) "nounmount", don't expire this mount (same as setting the
autofs timeout to 0 except only for this specific mount) .
3) "utimeout=<seconds>", expire this mount using the specified
timeout (again same as setting the autofs timeout but only for
this mount)

To implement these options per-dentry expire timeouts need to be
implemented for autofs indirect mounts. This is because all map
keys (mounts) for autofs indirect mounts use an expire timeout
stored in the autofs mount super block info. structure and all
indirect mounts use the same expire timeout.

Fixes:

- Fix missing fput for FSCONFIG_SET_FD in autofs

- Use param->file for FSCONFIG_SET_FD in coda

- Delete the 'fs/netfs' proc subtreee when netfs module exits

- Make sure that struct uid_gid_map fits into a single cacheline

- Don't flush in-flight wb switches for superblocks without cgroup
writeback

- Correcting the idmapping mount example in the idmapping
documentation

- Fix a race between evice_inodes() and find_inode() and iput()

- Refine the show_inode_state() macro definition in writeback code

- Prevent dump_mapping() from accessing invalid dentry.d_name.name

- Show actual source for debugfs in /proc/mounts

- Annotate data-race of busy_poll_usecs in eventpoll

- Don't WARN for racy path_noexec check in exec code

- Handle OOM on mnt_warn_timestamp_expiry()

- Fix some spelling in the iomap design documentation

- Fix typo in procfs comment

- Fix typo in fs/namespace.c comment

Cleanups:

- Add the VFS git tree to the MAINTAINERS file

- Move FMODE_UNSIGNED_OFFSET to fop_flags freeing up another f_mode
bit in struct file bringing us to 5 free f_mode bits

- Remove the __I_DIO_WAKEUP bit from i_state flags as we can simplify
the wait mechanism

- Remove the unused path_put_init() helper

- Replace a __u32 with u32 for s_fsnotify_mask as __u32 is uapi
specific

- Replace the unsigned long i_state member with a u32 i_state member
in struct inode freeing up 4 bytes in struct inode. Instead of
using the bit based wait apis we're now using the var event apis
and using the individual bytes of the i_state member to wait on
state changes

- Explain how per-syscall AT_* flags should be allocated

- Use in_group_or_capable() helper to simplify the posix acl mode
update code

- Switch to LIST_HEAD() in fsync_buffers_list() to simplify the code

- Removed comment about d_rcu_to_refcount() as that function doesn't
exist anymore

- Add kernel documentation for lookup_fast()

- Don't re-zero evenpoll fields

- Remove outdated comment after close_fd()

- Fix imprecise wording in comment about the pipe filesystem

- Drop GFP_NOFAIL mode from alloc_page_buffers

- Missing blank line warnings and struct declaration improved in
file_table

- Annotate struct poll_list with __counted_by()

- Remove the unused read parameter in percpu-rwsem

- Remove linux/prefetch.h include from direct-io code

- Use kmemdup_array instead of kmemdup for multiple allocation in
mnt_idmapping code

- Remove unused mnt_cursor_del() declaration

Performance tweaks:

- Dodge smp_mb in break_lease and break_deleg in the common case

- Only read fops once in fops_{get,put}()

- Use RCU in ilookup()

- Elide smp_mb in iversion handling in the common case

- Drop one lock trip in evict()"

* tag 'vfs-6.12.misc' of gitolite.kernel.org:pub/scm/linux/kernel/git/vfs/vfs: (58 commits)
uidgid: make sure we fit into one cacheline
proc: Fix typo in the comment
fs/pipe: Correct imprecise wording in comment
fhandle: expose u64 mount id to name_to_handle_at(2)
uapi: explain how per-syscall AT_* flags should be allocated
fs: drop GFP_NOFAIL mode from alloc_page_buffers
writeback: Refine the show_inode_state() macro definition
fs/inode: Prevent dump_mapping() accessing invalid dentry.d_name.name
mnt_idmapping: Use kmemdup_array instead of kmemdup for multiple allocation
netfs: Delete subtree of 'fs/netfs' when netfs module exits
fs: use LIST_HEAD() to simplify code
inode: make i_state a u32
inode: port __I_LRU_ISOLATING to var event
vfs: fix race between evice_inodes() and find_inode()&iput()
inode: port __I_NEW to var event
inode: port __I_SYNC to var event
fs: reorder i_state bits
fs: add i_state helpers
MAINTAINERS: add the VFS git tree
fs: s/__u32/u32/ for s_fsnotify_mask
...

show more ...

fs: Fix file_set_fowner LSM hook inconsistencies

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

fs: Fix file_set_fowner LSM hook inconsistencies

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 <viro@zeniv.linux.org.uk>
Cc: Casey Schaufler <casey@schaufler-ca.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: James Morris <jmorris@namei.org>
Cc: Jann Horn <jannh@google.com>
Cc: Ondrej Mosnacek <omosnace@redhat.com>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Serge E. Hallyn <serge@hallyn.com>
Cc: Stephen Smalley <stephen.smalley.work@gmail.com>
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Paul Moore <paul@paul-moore.com>

show more ...

file: reclaim 24 bytes from f_owner

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'

file: reclaim 24 bytes from f_owner

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 <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

show more ...

fcntl: add F_CREATED_QUERY

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_

fcntl: add F_CREATED_QUERY

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 <jlayton@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>

show more ...

Merge branch 'next' into for-linus

Prepare input updates for 6.11 merge window.

Merge tag 'v6.9' into next

Sync up with the mainline to bring in the new cleanup API.

Merge drm-misc-next-2024-07-04 into drm-misc-next-fixes

Let's start the drm-misc-next-fixes cycle.

Signed-off-by: Maxime Ripard <mripard@kernel.org>

Merge drm/drm-next into drm-intel-next

Sync to v6.10-rc3.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>

Merge drm/drm-next into drm-xe-next

Needed to get tracing cleanup and add mmio tracing series.

Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

Merge remote-tracking branch 'drm-misc/drm-misc-next' into HEAD

Merge drm-misc-next tree into the msm-next tree in order to be able to
use HDMI connector framework for the MSM HDMI driver.

Merge drm/drm-next into drm-misc-next

Let's start the new release cycle.

Signed-off-by: Maxime Ripard <mripard@kernel.org>

Merge drm/drm-next into drm-intel-gt-next

Some display refactoring patches are needed in order to allow conflict-
less merging.

Signed-off-by: Tvrtko Ursulin <tursulin@ursulin.net>

Merge branch 'tip/x86/cpu'

The Lunarlake patches rely on the new VFM stuff.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>

Merge topic branches 'clkdev' and 'fixes' into for-linus

Merge remote-tracking branch 'drm/drm-fixes' into drm-misc-fixes

v6.10-rc1 is released, forward from v6.9

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

Merge branch 'master' into mm-stable