As Linus suggested this enables pidfs unconditionally. A key property to
retain is the ability to compare pidfds by inode number (cf. [1]).
That's extremely helpful just as comparing namespace file descriptors by
inode number is. They are used in a variety of scenarios where they need
to be compared, e.g., when receiving a pidfd via SO_PEERPIDFD from a
socket to trivially authenticate a the sender and various other
use-cases.
For 64bit systems this is pretty trivial to do. For 32bit it's slightly
more annoying as we discussed but we simply add a dumb ida based
allocator that gets used on 32bit. This gives the same guarantees about
inode numbers on 64bit without any overflow risk. Practically, we'll
never run into overflow issues because we're constrained by the number
of processes that can exist on 32bit and by the number of open files
that can exist on a 32bit system. On 64bit none of this matters and
things are very simple.
If 32bit also needs the uniqueness guarantee they can simply parse the
contents of /proc/<pid>/fd/<nr>. The uniqueness guarantees have a
variety of use-cases. One of the most obvious ones is that they will
make pidfiles (or "pidfdfiles", I guess) reliable as the unique
identifier can be placed into there that won't be reycled. Also a
frequent request.
Note, I took the chance and simplified path_from_stashed() even further.
Instead of passing the inode number explicitly to path_from_stashed() we
let the filesystem handle that internally. So path_from_stashed() ends
up even simpler than it is now. This is also a good solution allowing
the cleanup code to be clean and consistent between 32bit and 64bit. The
cleanup path in prepare_anon_dentry() is also switched around so we put
the inode before the dentry allocation. This means we only have to call
the cleanup handler for the filesystem's inode data once and can rely
->evict_inode() otherwise.
Aside from having to have a bit of extra code for 32bit it actually ends
up a nice cleanup for path_from_stashed() imho.
Tested on both 32 and 64bit including error injection.
Link: https://github.com/systemd/systemd/pull/31713 [1]
Link: https://lore.kernel.org/r/20240312-dingo-sehnlich-b3ecc35c6de7@brauner
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-----BEGIN PGP SIGNATURE-----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=Hy//
-----END PGP SIGNATURE-----
Merge tag 'for-6.9/io_uring-20240310' of git://git.kernel.dk/linux
Pull io_uring updates from Jens Axboe:
- Make running of task_work internal loops more fair, and unify how the
different methods deal with them (me)
- Support for per-ring NAPI. The two minor networking patches are in a
shared branch with netdev (Stefan)
- Add support for truncate (Tony)
- Export SQPOLL utilization stats (Xiaobing)
- Multishot fixes (Pavel)
- Fix for a race in manipulating the request flags via poll (Pavel)
- Cleanup the multishot checking by making it generic, moving it out of
opcode handlers (Pavel)
- Various tweaks and cleanups (me, Kunwu, Alexander)
* tag 'for-6.9/io_uring-20240310' of git://git.kernel.dk/linux: (53 commits)
io_uring: Fix sqpoll utilization check racing with dying sqpoll
io_uring/net: dedup io_recv_finish req completion
io_uring: refactor DEFER_TASKRUN multishot checks
io_uring: fix mshot io-wq checks
io_uring/net: add io_req_msg_cleanup() helper
io_uring/net: simplify msghd->msg_inq checking
io_uring/kbuf: rename REQ_F_PARTIAL_IO to REQ_F_BL_NO_RECYCLE
io_uring/net: remove dependency on REQ_F_PARTIAL_IO for sr->done_io
io_uring/net: correctly handle multishot recvmsg retry setup
io_uring/net: clear REQ_F_BL_EMPTY in the multishot retry handler
io_uring: fix io_queue_proc modifying req->flags
io_uring: fix mshot read defer taskrun cqe posting
io_uring/net: fix overflow check in io_recvmsg_mshot_prep()
io_uring/net: correct the type of variable
io_uring/sqpoll: statistics of the true utilization of sq threads
io_uring/net: move recv/recvmsg flags out of retry loop
io_uring/kbuf: flag request if buffer pool is empty after buffer pick
io_uring/net: improve the usercopy for sendmsg/recvmsg
io_uring/net: move receive multishot out of the generic msghdr path
io_uring/net: unify how recvmsg and sendmsg copy in the msghdr
...
Right now we pass a bunch of info that is fs specific which doesn't make
a lot of sense and it bleeds fs sepcific details into the generic
helper. nsfs and pidfs have slightly different needs when initializing
inodes. Add simple operations that are stashed in sb->s_fs_info that
both can implement. This also allows us to get rid of cleaning up
references in the caller. All in all path_from_stashed() becomes way
simpler.
Signed-off-by: Christian Brauner <brauner@kernel.org>
Both pidfs and nsfs use a memory location to stash a dentry for reuse by
concurrent openers. Right now two custom
dentry->d_prune::{ns,pidfs}_prune_dentry() methods are needed that do
the same thing. The only thing that differs is that they need to get to
the memory location to store or retrieve the dentry from differently.
Fix that by remember the stashing location for the dentry in
dentry->d_fsdata which allows us to retrieve it in dentry->d_prune. That
in turn makes it possible to add a common helper that pidfs and nsfs can
both use.
Link: https://lore.kernel.org/r/CAHk-=wg8cHY=i3m6RnXQ2Y2W8psicKWQEZq1=94ivUiviM-0OA@mail.gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
Moving pidfds from the anonymous inode infrastructure to a separate tiny
in-kernel filesystem similar to sockfs, pipefs, and anon_inodefs causes
selinux denials and thus various userspace components that make heavy
use of pidfds to fail as pidfds used anon_inode_getfile() which aren't
subject to any LSM hooks. But dentry_open() is and that would cause
regressions.
The failures that are seen are selinux denials. But the core failure is
dbus-broker. That cascades into other services failing that depend on
dbus-broker. For example, when dbus-broker fails to start polkit and all
the others won't be able to work because they depend on dbus-broker.
The reason for dbus-broker failing is because it doesn't handle failures
for SO_PEERPIDFD correctly. Last kernel release we introduced
SO_PEERPIDFD (and SCM_PIDFD). SO_PEERPIDFD allows dbus-broker and polkit
and others to receive a pidfd for the peer of an AF_UNIX socket. This is
the first time in the history of Linux that we can safely authenticate
clients in a race-free manner.
dbus-broker immediately made use of this but messed up the error
checking. It only allowed EINVAL as a valid failure for SO_PEERPIDFD.
That's obviously problematic not just because of LSM denials but because
of seccomp denials that would prevent SO_PEERPIDFD from working; or any
other new error code from there.
So this is catching a flawed implementation in dbus-broker as well. It
has to fallback to the old pid-based authentication when SO_PEERPIDFD
doesn't work no matter the reasons otherwise it'll always risk such
failures. So overall that LSM denial should not have caused dbus-broker
to fail. It can never assume that a feature released one kernel ago like
SO_PEERPIDFD can be assumed to be available.
So, the next fix separate from the selinux policy update is to try and
fix dbus-broker at [3]. That should make it into Fedora as well. In
addition the selinux reference policy should also be updated. See [4]
for that. If Selinux is in enforcing mode in userspace and it encounters
anything that it doesn't know about it will deny it by default. And the
policy is entirely in userspace including declaring new types for stuff
like nsfs or pidfs to allow it.
For now we continue to raise S_PRIVATE on the inode if it's a pidfs
inode which means things behave exactly like before.
Link: https://bugzilla.redhat.com/show_bug.cgi?id=2265630
Link: https://github.com/fedora-selinux/selinux-policy/pull/2050
Link: https://github.com/bus1/dbus-broker/pull/343 [3]
Link: https://github.com/SELinuxProject/refpolicy/pull/762 [4]
Reported-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20240222190334.GA412503@dev-arch.thelio-3990X
Link: https://lore.kernel.org/r/20240218-neufahrzeuge-brauhaus-fb0eb6459771@brauner
Signed-off-by: Christian Brauner <brauner@kernel.org>
do_sys_ftruncate receives a file descriptor, fgets the struct file, and
finally actually truncates the file.
do_ftruncate allows for passing in a file directly, with the caller
already holding a reference to it.
Signed-off-by: Tony Solomonik <tony.solomonik@gmail.com>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Link: https://lore.kernel.org/r/20240202121724.17461-2-tony.solomonik@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
change of locking rules for __dentry_kill(), regularized refcounting
rules in that area, assorted cleanups and removal of weird corner
cases (e.g. now ->d_iput() on child is always called before the parent
might hit __dentry_kill(), etc.)
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
-----BEGIN PGP SIGNATURE-----
iHUEABYIAB0WIQQqUNBr3gm4hGXdBJlZ7Krx/gZQ6wUCZZ+sQQAKCRBZ7Krx/gZQ
6ybjAQDM5jiS93IUzfHjCWq0nVBX5YGbDAkZOeqxbmIdQb+2UAEA6elP5r0fBBcA
seo3bry4DirQMDaA/Cjh4+8r71YSOQs=
=7+Hk
-----END PGP SIGNATURE-----
Merge tag 'pull-dcache' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull dcache updates from Al Viro:
"Change of locking rules for __dentry_kill(), regularized refcounting
rules in that area, assorted cleanups and removal of weird corner
cases (e.g. now ->d_iput() on child is always called before the parent
might hit __dentry_kill(), etc)"
* tag 'pull-dcache' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (40 commits)
dcache: remove unnecessary NULL check in dget_dlock()
kill DCACHE_MAY_FREE
__d_unalias() doesn't use inode argument
d_alloc_parallel(): in-lookup hash insertion doesn't need an RCU variant
get rid of DCACHE_GENOCIDE
d_genocide(): move the extern into fs/internal.h
simple_fill_super(): don't bother with d_genocide() on failure
nsfs: use d_make_root()
d_alloc_pseudo(): move setting ->d_op there from the (sole) caller
kill d_instantate_anon(), fold __d_instantiate_anon() into remaining caller
retain_dentry(): introduce a trimmed-down lockless variant
__dentry_kill(): new locking scheme
d_prune_aliases(): use a shrink list
switch select_collect{,2}() to use of to_shrink_list()
to_shrink_list(): call only if refcount is 0
fold dentry_kill() into dput()
don't try to cut corners in shrink_lock_dentry()
fold the call of retain_dentry() into fast_dput()
Call retain_dentry() with refcount 0
dentry_kill(): don't bother with retain_dentry() on slow path
...
broken in 6.5; we really can't lock two unrelated directories
without holding ->s_vfs_rename_mutex first and in case of
same-parent rename of a subdirectory 6.5 ends up doing just
that.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
-----BEGIN PGP SIGNATURE-----
iHUEABYIAB0WIQQqUNBr3gm4hGXdBJlZ7Krx/gZQ6wUCZZ+lyQAKCRBZ7Krx/gZQ
60MWAP94hTqeMIpjhsUIkrTnylrIFaiw4UCWFJzIRG1QQYKqCgD/XUaWI9np7dL6
0wR/j4CQSdJjiEFKUFE2pD3QoSuJYAQ=
=+x0+
-----END PGP SIGNATURE-----
Merge tag 'pull-rename' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull rename updates from Al Viro:
"Fix directory locking scheme on rename
This was broken in 6.5; we really can't lock two unrelated directories
without holding ->s_vfs_rename_mutex first and in case of same-parent
rename of a subdirectory 6.5 ends up doing just that"
* tag 'pull-rename' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
rename(): avoid a deadlock in the case of parents having no common ancestor
kill lock_two_inodes()
rename(): fix the locking of subdirectories
f2fs: Avoid reading renamed directory if parent does not change
ext4: don't access the source subdirectory content on same-directory rename
ext2: Avoid reading renamed directory if parent does not change
udf_rename(): only access the child content on cross-directory rename
ocfs2: Avoid touching renamed directory if parent does not change
reiserfs: Avoid touching renamed directory if parent does not change
-----BEGIN PGP SIGNATURE-----
iHUEABYKAB0WIQRAhzRXHqcMeLMyaSiRxhvAZXjcogUCZZUzXQAKCRCRxhvAZXjc
ogOtAQDpqUp1zY4dV/dZisCJ5xarZTsSZ1AvgmcxZBtS0NhbdgEAshWvYGA9ryS/
ChL5jjtjjZDLhRA//reoFHTQIrdp2w8=
=bF+R
-----END PGP SIGNATURE-----
Merge tag 'vfs-6.8.rw' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull vfs rw updates from Christian Brauner:
"This contains updates from Amir for read-write backing file helpers
for stacking filesystems such as overlayfs:
- Fanotify is currently in the process of introducing pre content
events. Roughly, a new permission event will be added indicating
that it is safe to write to the file being accessed. These events
are used by hierarchical storage managers to e.g., fill the content
of files on first access.
During that work we noticed that our current permission checking is
inconsistent in rw_verify_area() and remap_verify_area().
Especially in the splice code permission checking is done multiple
times. For example, one time for the whole range and then again for
partial ranges inside the iterator.
In addition, we mostly do permission checking before we call
file_start_write() except for a few places where we call it after.
For pre-content events we need such permission checking to be done
before file_start_write(). So this is a nice reason to clean this
all up.
After this series, all permission checking is done before
file_start_write().
As part of this cleanup we also massaged the splice code a bit. We
got rid of a few helpers because we are alredy drowning in special
read-write helpers. We also cleaned up the return types for splice
helpers.
- Introduce generic read-write helpers for backing files. This lifts
some overlayfs code to common code so it can be used by the FUSE
passthrough work coming in over the next cycles. Make Amir and
Miklos the maintainers for this new subsystem of the vfs"
* tag 'vfs-6.8.rw' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (30 commits)
fs: fix __sb_write_started() kerneldoc formatting
fs: factor out backing_file_mmap() helper
fs: factor out backing_file_splice_{read,write}() helpers
fs: factor out backing_file_{read,write}_iter() helpers
fs: prepare for stackable filesystems backing file helpers
fsnotify: optionally pass access range in file permission hooks
fsnotify: assert that file_start_write() is not held in permission hooks
fsnotify: split fsnotify_perm() into two hooks
fs: use splice_copy_file_range() inline helper
splice: return type ssize_t from all helpers
fs: use do_splice_direct() for nfsd/ksmbd server-side-copy
fs: move file_start_write() into direct_splice_actor()
fs: fork splice_file_range() from do_splice_direct()
fs: create {sb,file}_write_not_started() helpers
fs: create file_write_started() helper
fs: create __sb_write_started() helper
fs: move kiocb_start_write() into vfs_iocb_iter_write()
fs: move permission hook out of do_iter_read()
fs: move permission hook out of do_iter_write()
fs: move file_start_write() into vfs_iter_write()
...
-----BEGIN PGP SIGNATURE-----
iHUEABYKAB0WIQRAhzRXHqcMeLMyaSiRxhvAZXjcogUCZZU0CgAKCRCRxhvAZXjc
osncAQDSJK0frJL+72NqXxa4YNzivrnuw6fhp5iaDAEqxdm8ygEAoJWyh7Rmkt8G
drAXWGyGnCYqv7UgC6axLyciid7TxQg=
=vJuv
-----END PGP SIGNATURE-----
Merge tag 'vfs-6.8.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull vfs mount updates from Christian Brauner:
"This contains the work to retrieve detailed information about mounts
via two new system calls. This is hopefully the beginning of the end
of the saga that started with fsinfo() years ago.
The LWN articles in [1] and [2] can serve as a summary so we can avoid
rehashing everything here.
At LSFMM in May 2022 we got into a room and agreed on what we want to
do about fsinfo(). Basically, split it into pieces. This is the first
part of that agreement. Specifically, it is concerned with retrieving
information about mounts. So this only concerns the mount information
retrieval, not the mount table change notification, or the extended
filesystem specific mount option work. That is separate work.
Currently mounts have a 32bit id. Mount ids are already in heavy use
by libmount and other low-level userspace but they can't be relied
upon because they're recycled very quickly. We agreed that mounts
should carry a unique 64bit id by which they can be referenced
directly. This is now implemented as part of this work.
The new 64bit mount id is exposed in statx() through the new
STATX_MNT_ID_UNIQUE flag. If the flag isn't raised the old mount id is
returned. If it is raised and the kernel supports the new 64bit mount
id the flag is raised in the result mask and the new 64bit mount id is
returned. New and old mount ids do not overlap so they cannot be
conflated.
Two new system calls are introduced that operate on the 64bit mount
id: statmount() and listmount(). A summary of the api and usage can be
found on LWN as well (cf. [3]) but of course, I'll provide a summary
here as well.
Both system calls rely on struct mnt_id_req. Which is the request
struct used to pass the 64bit mount id identifying the mount to
operate on. It is extensible to allow for the addition of new
parameters and for future use in other apis that make use of mount
ids.
statmount() mimicks the semantics of statx() and exposes a set flags
that userspace may raise in mnt_id_req to request specific information
to be retrieved. A statmount() call returns a struct statmount filled
in with information about the requested mount. Supported requests are
indicated by raising the request flag passed in struct mnt_id_req in
the @mask argument in struct statmount.
Currently we do support:
- STATMOUNT_SB_BASIC:
Basic filesystem info
- STATMOUNT_MNT_BASIC
Mount information (mount id, parent mount id, mount attributes etc)
- STATMOUNT_PROPAGATE_FROM
Propagation from what mount in current namespace
- STATMOUNT_MNT_ROOT
Path of the root of the mount (e.g., mount --bind /bla /mnt returns /bla)
- STATMOUNT_MNT_POINT
Path of the mount point (e.g., mount --bind /bla /mnt returns /mnt)
- STATMOUNT_FS_TYPE
Name of the filesystem type as the magic number isn't enough due to submounts
The string options STATMOUNT_MNT_{ROOT,POINT} and STATMOUNT_FS_TYPE
are appended to the end of the struct. Userspace can use the offsets
in @fs_type, @mnt_root, and @mnt_point to reference those strings
easily.
The struct statmount reserves quite a bit of space currently for
future extensibility. This isn't really a problem and if this bothers
us we can just send a follow-up pull request during this cycle.
listmount() is given a 64bit mount id via mnt_id_req just as
statmount(). It takes a buffer and a size to return an array of the
64bit ids of the child mounts of the requested mount. Userspace can
thus choose to either retrieve child mounts for a mount in batches or
iterate through the child mounts. For most use-cases it will be
sufficient to just leave space for a few child mounts. But for big
mount tables having an iterator is really helpful. Iterating through a
mount table works by setting @param in mnt_id_req to the mount id of
the last child mount retrieved in the previous listmount() call"
Link: https://lwn.net/Articles/934469 [1]
Link: https://lwn.net/Articles/829212 [2]
Link: https://lwn.net/Articles/950569 [3]
* tag 'vfs-6.8.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
add selftest for statmount/listmount
fs: keep struct mnt_id_req extensible
wire up syscalls for statmount/listmount
add listmount(2) syscall
statmount: simplify string option retrieval
statmount: simplify numeric option retrieval
add statmount(2) syscall
namespace: extract show_path() helper
mounts: keep list of mounts in an rbtree
add unique mount ID
Only io_uring uses __close_fd_get_file(). All it does is hide
current->files but io_uring accesses files_struct directly right now
anyway so it's a bit pointless. Just rename pick_file() to
file_close_fd_locked() and let io_uring use it. Add a lockdep assert in
there that we expect the caller to hold file_lock while we're at it.
Link: https://lore.kernel.org/r/20231130-vfs-files-fixes-v1-2-e73ca6f4ea83@kernel.org
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
A file that has never gotten FMODE_OPENED will never have RCU-accessed
references, its final fput() is equivalent to file_free() and if it
doesn't have FMODE_BACKING either, it can be done from any context and
won't need task_work treatment.
Now that we have SLAB_TYPESAFE_BY_RCU we can simplify this and have
other callers benefit. All of that can be achieved easier is to make
fput() recoginze that case and call file_free() directly.
No need to introduce a special primitive for that. It also allowed
things like failing dentry_open() could benefit from that as well.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
[Christian Brauner <brauner@kernel.org>: massage commit message]
Link: https://lore.kernel.org/r/20231126020834.GC38156@ZenIV
Signed-off-by: Christian Brauner <brauner@kernel.org>
There's only one caller left (lock_two_nondirectories()), and it
needs less complexity. Fold lock_two_inodes() in there and
simplify.
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
d_instantiate_unique() had been gone for 7 years; __d_lookup...()
and shrink_dcache_for_umount() are fs/internal.h fodder.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
A backing file struct stores two path's, one "real" path that is referring
to f_inode and one "fake" path, which should be displayed to users in
/proc/<pid>/maps.
There is a lot more potential code that needs to know the "real" path, then
code that needs to know the "fake" path.
Instead of code having to request the "real" path with file_real_path(),
store the "real" path in f_path and require code that needs to know the
"fake" path request it with file_user_path().
Replace the file_real_path() helper with a simple const accessor f_path().
After this change, file_dentry() is not expected to observe any files
with overlayfs f_path and real f_inode, so the call to ->d_real() should
not be needed. Leave the ->d_real() call for now and add an assertion
in ovl_d_real() to catch if we made wrong assumptions.
Suggested-by: Miklos Szeredi <miklos@szeredi.hu>
Link: https://lore.kernel.org/r/CAJfpegtt48eXhhjDFA1ojcHPNKj3Go6joryCPtEFAKpocyBsnw@mail.gmail.com/
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Link: https://lore.kernel.org/r/20231009153712.1566422-4-amir73il@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
A writeable mapped backing file can perform writes to the real inode.
Therefore, the real path mount must be kept writable so long as the
writable map exists.
This may not be strictly needed for ovelrayfs private upper mount,
but it is correct to take the mnt_writers count in the vfs helper.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Link: https://lore.kernel.org/r/20231009153712.1566422-2-amir73il@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
Failed opens (mostly ENOENT) legitimately happen a lot, for example here
are stats from stracing kernel build for few seconds (strace -fc make):
% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ------------------
0.76 0.076233 5 15040 3688 openat
(this is tons of header files tried in different paths)
In the common case of there being nothing to close (only the file object
to free) there is a lot of overhead which can be avoided.
This is most notably delegation of freeing to task_work, which comes
with an enormous cost (see 021a160abf ("fs: use __fput_sync in
close(2)" for an example).
Benchmarked with will-it-scale with a custom testcase based on
tests/open1.c, stuffed into tests/openneg.c:
[snip]
while (1) {
int fd = open("/tmp/nonexistent", O_RDONLY);
assert(fd == -1);
(*iterations)++;
}
[/snip]
Sapphire Rapids, openneg_processes -t 1 (ops/s):
before: 1950013
after: 2914973 (+49%)
file refcount is checked as a safety belt against buggy consumers with
an atomic cmpxchg. Technically it is not necessary, but it happens to
not be measurable due to several other atomics which immediately follow.
Optmizing them away to make this atomic into a problem is left as an
exercise for the reader.
v2:
- unexport fput_badopen and move to fs/internal.h
- handle the refcount with cmpxchg, adjust commentary accordingly
- tweak the commit message
Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Link: https://lore.kernel.org/r/20230926162228.68666-1-mjguzik@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
Before exporting these helpers to modules, make their names more
meaningful.
The names mnt_{get,put)_write_access*() were chosen, because they rhyme
with the inode {get,put)_write_access() helpers, which have a very close
meaning for the inode object.
Suggested-by: Christian Brauner <brauner@kernel.org>
Link: https://lore.kernel.org/r/20230817-anfechtbar-ruhelosigkeit-8c6cca8443fc@brauner/
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Message-Id: <20230908132900.2983519-2-amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
-----BEGIN PGP SIGNATURE-----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=p1bd
-----END PGP SIGNATURE-----
Merge tag 'for-6.6/block-2023-08-28' of git://git.kernel.dk/linux
Pull block updates from Jens Axboe:
"Pretty quiet round for this release. This contains:
- Add support for zoned storage to ublk (Andreas, Ming)
- Series improving performance for drivers that mark themselves as
needing a blocking context for issue (Bart)
- Cleanup the flush logic (Chengming)
- sed opal keyring support (Greg)
- Fixes and improvements to the integrity support (Jinyoung)
- Add some exports for bcachefs that we can hopefully delete again in
the future (Kent)
- deadline throttling fix (Zhiguo)
- Series allowing building the kernel without buffer_head support
(Christoph)
- Sanitize the bio page adding flow (Christoph)
- Write back cache fixes (Christoph)
- MD updates via Song:
- Fix perf regression for raid0 large sequential writes (Jan)
- Fix split bio iostat for raid0 (David)
- Various raid1 fixes (Heinz, Xueshi)
- raid6test build fixes (WANG)
- Deprecate bitmap file support (Christoph)
- Fix deadlock with md sync thread (Yu)
- Refactor md io accounting (Yu)
- Various non-urgent fixes (Li, Yu, Jack)
- Various fixes and cleanups (Arnd, Azeem, Chengming, Damien, Li,
Ming, Nitesh, Ruan, Tejun, Thomas, Xu)"
* tag 'for-6.6/block-2023-08-28' of git://git.kernel.dk/linux: (113 commits)
block: use strscpy() to instead of strncpy()
block: sed-opal: keyring support for SED keys
block: sed-opal: Implement IOC_OPAL_REVERT_LSP
block: sed-opal: Implement IOC_OPAL_DISCOVERY
blk-mq: prealloc tags when increase tagset nr_hw_queues
blk-mq: delete redundant tagset map update when fallback
blk-mq: fix tags leak when shrink nr_hw_queues
ublk: zoned: support REQ_OP_ZONE_RESET_ALL
md: raid0: account for split bio in iostat accounting
md/raid0: Fix performance regression for large sequential writes
md/raid0: Factor out helper for mapping and submitting a bio
md raid1: allow writebehind to work on any leg device set WriteMostly
md/raid1: hold the barrier until handle_read_error() finishes
md/raid1: free the r1bio before waiting for blocked rdev
md/raid1: call free_r1bio() before allow_barrier() in raid_end_bio_io()
blk-cgroup: Fix NULL deref caused by blkg_policy_data being installed before init
drivers/rnbd: restore sysfs interface to rnbd-client
md/raid5-cache: fix null-ptr-deref for r5l_flush_stripe_to_raid()
raid6: test: only check for Altivec if building on powerpc hosts
raid6: test: make sure all intermediate and artifact files are .gitignored
...
Make the naming consistent with the earlier introduced
super_lock_{read,write}() helpers.
Reviewed-by: Jan Kara <jack@suse.cz>
Message-Id: <20230818-vfs-super-fixes-v3-v3-2-9f0b1876e46b@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
kill_dirty has always been true for a long time, so hard code it and
remove the unused return value.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Message-Id: <20230811100828.1897174-18-hch@lst.de>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Fold emergency_thaw_bdev into it's only caller, to prepare for buffer.c
to be built only when buffer_head support is enabled.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Link: https://lore.kernel.org/r/20230801172201.1923299-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
-----BEGIN PGP SIGNATURE-----
iHUEABYKAB0WIQRAhzRXHqcMeLMyaSiRxhvAZXjcogUCZJU4WgAKCRCRxhvAZXjc
oofvAQDs9RJwQUyWHJmQA+tWz5cUE5DviVWCwwul5dQRRCqgaQEA2OIO0gPFaVoq
1OYOeLyUjl/cpS8e3u4uJtw34jttdQA=
=AwcR
-----END PGP SIGNATURE-----
Merge tag 'v6.5/vfs.file' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull vfs file handling updates from Christian Brauner:
"This contains Amir's work to fix a long-standing problem where an
unprivileged overlayfs mount can be used to avoid fanotify permission
events that were requested for an inode or superblock on the
underlying filesystem.
Some background about files opened in overlayfs. If a file is opened
in overlayfs @file->f_path will refer to a "fake" path. What this
means is that while @file->f_inode will refer to inode of the
underlying layer, @file->f_path refers to an overlayfs
{dentry,vfsmount} pair. The reasons for doing this are out of scope
here but it is the reason why the vfs has been providing the
open_with_fake_path() helper for overlayfs for very long time now. So
nothing new here.
This is for sure not very elegant and everyone including the overlayfs
maintainers agree. Improving this significantly would involve more
fragile and potentially rather invasive changes.
In various codepaths access to the path of the underlying filesystem
is needed for such hybrid file. The best example is fsnotify where
this becomes security relevant. Passing the overlayfs
@file->f_path->dentry will cause fsnotify to skip generating fsnotify
events registered on the underlying inode or superblock.
To fix this we extend the vfs provided open_with_fake_path() concept
for overlayfs to create a backing file container that holds the real
path and to expose a helper that can be used by relevant callers to
get access to the path of the underlying filesystem through the new
file_real_path() helper. This pattern is similar to what we do in
d_real() and d_real_inode().
The first beneficiary is fsnotify and fixes the security sensitive
problem mentioned above.
There's a couple of nice cleanups included as well.
Over time, the old open_with_fake_path() helper added specifically for
overlayfs a long time ago started to get used in other places such as
cachefiles. Even though cachefiles have nothing to do with hybrid
files.
The only reason cachefiles used that concept was that files opened
with open_with_fake_path() aren't charged against the caller's open
file limit by raising FMODE_NOACCOUNT. It's just mere coincidence that
both overlayfs and cachefiles need to ensure to not overcharge the
caller for their internal open calls.
So this work disentangles FMODE_NOACCOUNT use cases and backing file
use-cases by adding the FMODE_BACKING flag which indicates that the
file can be used to retrieve the backing file of another filesystem.
(Fyi, Jens will be sending you a really nice cleanup from Christoph
that gets rid of 3 FMODE_* flags otherwise this would be the last
fmode_t bit we'd be using.)
So now overlayfs becomes the sole user of the renamed
open_with_fake_path() helper which is now named backing_file_open().
For internal kernel users such as cachefiles that are only interested
in FMODE_NOACCOUNT but not in FMODE_BACKING we add a new
kernel_file_open() helper which opens a file without being charged
against the caller's open file limit. All new helpers are properly
documented and clearly annotated to mention their special uses.
We also rename vfs_tmpfile_open() to kernel_tmpfile_open() to clearly
distinguish it from vfs_tmpfile() and align it the other kernel_*()
internal helpers"
* tag 'v6.5/vfs.file' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
ovl: enable fsnotify events on underlying real files
fs: use backing_file container for internal files with "fake" f_path
fs: move kmem_cache_zalloc() into alloc_empty_file*() helpers
fs: use a helper for opening kernel internal files
fs: rename {vfs,kernel}_tmpfile_open()
-----BEGIN PGP SIGNATURE-----
iHUEABYKAB0WIQRAhzRXHqcMeLMyaSiRxhvAZXjcogUCZJU4NwAKCRCRxhvAZXjc
ordqAP0RmZEkUA5p98pK+0FEFIsS2S8qChh6YHQHP+hF606FGgEAivb3UPRm9p58
kRb5yK0/oXDUxGv7A+x+SIMVbcRyLgw=
=pi6N
-----END PGP SIGNATURE-----
Merge tag 'v6.5/vfs.rename.locking' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull vfs rename locking updates from Christian Brauner:
"This contains the work from Jan to fix problems with cross-directory
renames originally reported in [1].
To quickly sum it up some filesystems (so far we know at least about
ext4, udf, f2fs, ocfs2, likely also reiserfs, gfs2 and others) need to
lock the directory when it is being renamed into another directory.
This is because we need to update the parent pointer in the directory
in that case and if that races with other operations on the directory,
in particular a conversion from one directory format into another, bad
things can happen.
So far we've done the locking in the filesystem code but recently
Darrick pointed out in [2] that the RENAME_EXCHANGE case was missing.
That one is particularly nasty because RENAME_EXCHANGE can arbitrarily
mix regular files and directories and proper lock ordering is not
achievable in the filesystems alone.
This patch set adds locking into vfs_rename() so that not only parent
directories but also moved inodes, regardless of whether they are
directories or not, are locked when calling into the filesystem.
This means establishing a locking order for unrelated directories. New
helpers are added for this purpose and our documentation is updated to
cover this in detail.
The locking is now actually easier to follow as we now always lock
source and target. We've always locked the target independent of
whether it was a directory or file and we've always locked source if
it was a regular file. The exact details for why this came about can
be found in [3] and [4]"
Link: https://lore.kernel.org/all/20230117123735.un7wbamlbdihninm@quack3 [1]
Link: https://lore.kernel.org/all/20230517045836.GA11594@frogsfrogsfrogs [2]
Link: https://lore.kernel.org/all/20230526-schrebergarten-vortag-9cd89694517e@brauner [3]
Link: https://lore.kernel.org/all/20230530-seenotrettung-allrad-44f4b00139d4@brauner [4]
* tag 'v6.5/vfs.rename.locking' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
fs: Restrict lock_two_nondirectories() to non-directory inodes
fs: Lock moved directories
fs: Establish locking order for unrelated directories
Revert "f2fs: fix potential corruption when moving a directory"
Revert "udf: Protect rename against modification of moved directory"
ext4: Remove ext4 locking of moved directory
Provide helpers to set and clear sb->s_readonly_remount including
appropriate memory barriers. Also use this opportunity to document what
the barriers pair with and why they are needed.
Suggested-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Message-Id: <20230620112832.5158-1-jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Overlayfs uses open_with_fake_path() to allocate internal kernel files,
with a "fake" path - whose f_path is not on the same fs as f_inode.
Allocate a container struct backing_file for those internal files, that
is used to hold the "fake" ovl path along with the real path.
backing_file_real_path() can be used to access the stored real path.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Message-Id: <20230615112229.2143178-5-amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Currently the locking order of inode locks for directories that are not
in ancestor relationship is not defined because all operations that
needed to lock two directories like this were serialized by
sb->s_vfs_rename_mutex. However some filesystems need to lock two
subdirectories for RENAME_EXCHANGE operations and for this we need the
locking order established even for two tree-unrelated directories.
Provide a helper function lock_two_inodes() that establishes lock
ordering for any two inodes and use it in lock_two_directories().
CC: stable@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
Message-Id: <20230601105830.13168-4-jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
-----BEGIN PGP SIGNATURE-----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=DweL
-----END PGP SIGNATURE-----
Merge tag '6.4-rc-ksmbd-server-fixes' of git://git.samba.org/ksmbd
Pull ksmbd server updates from Steve French:
- SMB3.1.1 negotiate context fixes and cleanup
- new lock_rename_child VFS helper
- ksmbd fix to avoid unlink race and to use the new VFS helper to avoid
rename race
* tag '6.4-rc-ksmbd-server-fixes' of git://git.samba.org/ksmbd:
ksmbd: fix racy issue from using ->d_parent and ->d_name
ksmbd: remove unused compression negotiate ctx packing
ksmbd: avoid duplicate negotiate ctx offset increments
ksmbd: set NegotiateContextCount once instead of every inc
fs: introduce lock_rename_child() helper
ksmbd: remove internal.h include
Since vfs_path_lookup is exported, It should not be internal.
Move vfs_path_lookup prototype in internal.h to linux/namei.h.
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
We've aligned setgid behavior over multiple kernel releases. The details
can be found in the following two merge messages:
cf619f8919 ("Merge tag 'fs.ovl.setgid.v6.2')
426b4ca2d6 ("Merge tag 'fs.setgid.v6.0')
Consistent setgid stripping behavior is now encapsulated in the
setattr_should_drop_sgid() helper which is used by all filesystems that
strip setgid bits outside of vfs proper. Switch nfs to rely on this
helper as well. Without this patch the setgid stripping tests in
xfstests will fail.
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Message-Id: <20230313-fs-nfs-setgid-v2-1-9a59f436cfc0@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
-----BEGIN PGP SIGNATURE-----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=IU45
-----END PGP SIGNATURE-----
Merge tag 'for-6.3/dio-2023-02-16' of git://git.kernel.dk/linux
Pull legacy dio update from Jens Axboe:
"We only have a few file systems that use the old dio code, make them
select it rather than build it unconditionally"
* tag 'for-6.3/dio-2023-02-16' of git://git.kernel.dk/linux:
fs: build the legacy direct I/O code conditionally
fs: move sb_init_dio_done_wq out of direct-io.c
sb_init_dio_done_wq is also used by the iomap code, so move it to
super.c in preparation for building direct-io.c conditionally.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20230125065839.191256-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Now that we converted everything to just rely on struct mnt_idmap move it all
into a separate file. This ensure that no code can poke around in struct
mnt_idmap without any dedicated helpers and makes it easier to extend it in the
future. Filesystems will now not be able to conflate mount and filesystem
idmappings as they are two distinct types and require distinct helpers that
cannot be used interchangeably. We are now also able to extend struct mnt_idmap
as we see fit.
Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Convert to struct mnt_idmap.
Last cycle we merged the necessary infrastructure in
256c8aed2b ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.
Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.
Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.
Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Convert to struct mnt_idmap.
Last cycle we merged the necessary infrastructure in
256c8aed2b ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.
Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.
Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.
Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Convert an initial portion to rely on struct mnt_idmap by converting the
high level xattr helpers.
Reviewed-by: Seth Forshee (DigitalOcean) <sforshee@kernel.org>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
In previous patches we built a new posix api solely around get and set
inode operations. Now that we have all the pieces in place we can switch
the system calls and the vfs over to only rely on this api when
interacting with posix acls. This finally removes all type unsafety and
type conversion issues explained in detail in [1] that we aim to get rid
of.
With the new posix acl api we immediately translate into an appropriate
kernel internal struct posix_acl format both when getting and setting
posix acls. This is a stark contrast to before were we hacked unsafe raw
values into the uapi struct that was stored in a void pointer relying
and having filesystems and security modules hack around in the uapi
struct as well.
Link: https://lore.kernel.org/all/20220801145520.1532837-1-brauner@kernel.org [1]
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Split out the generic checks whether an inode allows writing xattrs. Since
security.* and system.* xattrs don't have any restrictions and we're going
to split out posix acls into a dedicated api we will use this helper to
check whether we can write posix acls.
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Currently setgid stripping in file_remove_privs()'s should_remove_suid()
helper is inconsistent with other parts of the vfs. Specifically, it only
raises ATTR_KILL_SGID if the inode is S_ISGID and S_IXGRP but not if the
inode isn't in the caller's groups and the caller isn't privileged over the
inode although we require this already in setattr_prepare() and
setattr_copy() and so all filesystem implement this requirement implicitly
because they have to use setattr_{prepare,copy}() anyway.
But the inconsistency shows up in setgid stripping bugs for overlayfs in
xfstests (e.g., generic/673, generic/683, generic/685, generic/686,
generic/687). For example, we test whether suid and setgid stripping works
correctly when performing various write-like operations as an unprivileged
user (fallocate, reflink, write, etc.):
echo "Test 1 - qa_user, non-exec file $verb"
setup_testfile
chmod a+rws $junk_file
commit_and_check "$qa_user" "$verb" 64k 64k
The test basically creates a file with 6666 permissions. While the file has
the S_ISUID and S_ISGID bits set it does not have the S_IXGRP set. On a
regular filesystem like xfs what will happen is:
sys_fallocate()
-> vfs_fallocate()
-> xfs_file_fallocate()
-> file_modified()
-> __file_remove_privs()
-> dentry_needs_remove_privs()
-> should_remove_suid()
-> __remove_privs()
newattrs.ia_valid = ATTR_FORCE | kill;
-> notify_change()
-> setattr_copy()
In should_remove_suid() we can see that ATTR_KILL_SUID is raised
unconditionally because the file in the test has S_ISUID set.
But we also see that ATTR_KILL_SGID won't be set because while the file
is S_ISGID it is not S_IXGRP (see above) which is a condition for
ATTR_KILL_SGID being raised.
So by the time we call notify_change() we have attr->ia_valid set to
ATTR_KILL_SUID | ATTR_FORCE. Now notify_change() sees that
ATTR_KILL_SUID is set and does:
ia_valid = attr->ia_valid |= ATTR_MODE
attr->ia_mode = (inode->i_mode & ~S_ISUID);
which means that when we call setattr_copy() later we will definitely
update inode->i_mode. Note that attr->ia_mode still contains S_ISGID.
Now we call into the filesystem's ->setattr() inode operation which will
end up calling setattr_copy(). Since ATTR_MODE is set we will hit:
if (ia_valid & ATTR_MODE) {
umode_t mode = attr->ia_mode;
vfsgid_t vfsgid = i_gid_into_vfsgid(mnt_userns, inode);
if (!vfsgid_in_group_p(vfsgid) &&
!capable_wrt_inode_uidgid(mnt_userns, inode, CAP_FSETID))
mode &= ~S_ISGID;
inode->i_mode = mode;
}
and since the caller in the test is neither capable nor in the group of the
inode the S_ISGID bit is stripped.
But assume the file isn't suid then ATTR_KILL_SUID won't be raised which
has the consequence that neither the setgid nor the suid bits are stripped
even though it should be stripped because the inode isn't in the caller's
groups and the caller isn't privileged over the inode.
If overlayfs is in the mix things become a bit more complicated and the bug
shows up more clearly. When e.g., ovl_setattr() is hit from
ovl_fallocate()'s call to file_remove_privs() then ATTR_KILL_SUID and
ATTR_KILL_SGID might be raised but because the check in notify_change() is
questioning the ATTR_KILL_SGID flag again by requiring S_IXGRP for it to be
stripped the S_ISGID bit isn't removed even though it should be stripped:
sys_fallocate()
-> vfs_fallocate()
-> ovl_fallocate()
-> file_remove_privs()
-> dentry_needs_remove_privs()
-> should_remove_suid()
-> __remove_privs()
newattrs.ia_valid = ATTR_FORCE | kill;
-> notify_change()
-> ovl_setattr()
// TAKE ON MOUNTER'S CREDS
-> ovl_do_notify_change()
-> notify_change()
// GIVE UP MOUNTER'S CREDS
// TAKE ON MOUNTER'S CREDS
-> vfs_fallocate()
-> xfs_file_fallocate()
-> file_modified()
-> __file_remove_privs()
-> dentry_needs_remove_privs()
-> should_remove_suid()
-> __remove_privs()
newattrs.ia_valid = attr_force | kill;
-> notify_change()
The fix for all of this is to make file_remove_privs()'s
should_remove_suid() helper to perform the same checks as we already
require in setattr_prepare() and setattr_copy() and have notify_change()
not pointlessly requiring S_IXGRP again. It doesn't make any sense in the
first place because the caller must calculate the flags via
should_remove_suid() anyway which would raise ATTR_KILL_SGID.
While we're at it we move should_remove_suid() from inode.c to attr.c
where it belongs with the rest of the iattr helpers. Especially since it
returns ATTR_KILL_S{G,U}ID flags. We also rename it to
setattr_should_drop_suidgid() to better reflect that it indicates both
setuid and setgid bit removal and also that it returns attr flags.
Running xfstests with this doesn't report any regressions. We should really
try and use consistent checks.
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
The current setgid stripping logic during write and ownership change
operations is inconsistent and strewn over multiple places. In order to
consolidate it and make more consistent we'll add a new helper
setattr_should_drop_sgid(). The function retains the old behavior where
we remove the S_ISGID bit unconditionally when S_IXGRP is set but also
when it isn't set and the caller is neither in the group of the inode
nor privileged over the inode.
We will use this helper both in write operation permission removal such
as file_remove_privs() as well as in ownership change operations.
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
In setattr_{copy,prepare}() we need to perform the same permission
checks to determine whether we need to drop the setgid bit or not.
Instead of open-coding it twice add a simple helper the encapsulates the
logic. We will reuse this helpers to make dropping the setgid bit during
write operations more consistent in a follow up patch.
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
passing kmap_local_page() result to __kernel_write() is unsafe -
random ->write_iter() might (and 9p one does) get unhappy when
passed ITER_KVEC with pointer that came from kmap_local_page().
Fix by providing a variant of __kernel_write() that takes an iov_iter
from caller (__kernel_write() becomes a trivial wrapper) and adding
dump_emit_page() that parallels dump_emit(), except that instead of
__kernel_write() it uses __kernel_write_iter() with ITER_BVEC source.
Fixes: 3159ed5779 "fs/coredump: use kmap_local_page()"
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Christian Brauner