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linux/fs
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Linus Torvalds 054aa8d439 fget: check that the fd still exists after getting a ref to it 
Jann Horn points out that there is another possible race wrt Unix domain
socket garbage collection, somewhat reminiscent of the one fixed in
commit cbcf01128d ("af_unix: fix garbage collect vs MSG_PEEK").

See the extended comment about the garbage collection requirements added
to unix_peek_fds() by that commit for details.

The race comes from how we can locklessly look up a file descriptor just
as it is in the process of being closed, and with the right artificial
timing (Jann added a few strategic 'mdelay(500)' calls to do that), the
Unix domain socket garbage collector could see the reference count
decrement of the close() happen before fget() took its reference to the
file and the file was attached onto a new file descriptor.

This is all (intentionally) correct on the 'struct file *' side, with
RCU lookups and lockless reference counting very much part of the
design.  Getting that reference count out of order isn't a problem per
se.

But the garbage collector can get confused by seeing this situation of
having seen a file not having any remaining external references and then
seeing it being attached to an fd.

In commit cbcf01128d ("af_unix: fix garbage collect vs MSG_PEEK") the
fix was to serialize the file descriptor install with the garbage
collector by taking and releasing the unix_gc_lock.

That's not really an option here, but since this all happens when we are
in the process of looking up a file descriptor, we can instead simply
just re-check that the file hasn't been closed in the meantime, and just
re-do the lookup if we raced with a concurrent close() of the same file
descriptor.

Reported-and-tested-by: Jann Horn <jannh@google.com>
Acked-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-12-03 10:06:58 -08:00
..
9p netfs, 9p, afs, ceph: Use folios 2021-11-10 21:16:56 +00:00
adfs mm: require ->set_page_dirty to be explicitly wired up 2021-06-29 10:53:48 -07:00
affs affs: use bdev_nr_sectors instead of open coding it 2021-10-18 14:43:22 -06:00
afs afs: Use folios in directory handling 2021-11-10 21:17:09 +00:00
autofs autofs: fix wait name hash calculation in autofs_wait() 2021-10-20 21:09:02 -04:00
befs isystem: ship and use stdarg.h 2021-08-19 09:02:55 +09:00
bfs mm: require ->set_page_dirty to be explicitly wired up 2021-06-29 10:53:48 -07:00
btrfs for-5.16-rc2-tag 2021-11-26 11:24:32 -08:00
cachefiles for-5.16/ki_complete-2021-10-29 2021-11-01 10:17:11 -07:00
ceph One notable change here is that async creates and unlinks introduced 2021-11-13 11:31:07 -08:00
cifs cifs: update internal version number 2021-11-23 10:07:15 -06:00
coda coda: bump module version to 7.2 2021-11-09 10:02:51 -08:00
configfs configfs: fix a race in configfs_lookup() 2021-08-25 07:58:49 +02:00
cramfs cramfs: use bdev_nr_bytes instead of open coding it 2021-10-18 14:43:22 -06:00
crypto fscrypt: improve a few comments 2021-10-25 19:11:50 -07:00
debugfs debugfs: debugfs_create_file_size(): use IS_ERR to check for error 2021-09-21 09:09:06 +02:00
devpts
dlm fs: dlm: avoid comms shutdown delay in release_lockspace 2021-09-01 11:29:14 -05:00
ecryptfs mm: require ->set_page_dirty to be explicitly wired up 2021-06-29 10:53:48 -07:00
efivarfs efivars: convert to fileattr 2021-04-12 15:04:29 +02:00
efs
erofs erofs: fix deadlock when shrink erofs slab 2021-11-23 14:58:16 +08:00
exfat exfat: fix incorrect loading of i_blocks for large files 2021-11-01 07:49:21 +09:00
exportfs
ext2 ext2: fix sleeping in atomic bugs on error 2021-09-22 13:05:23 +02:00
ext4 Only bug fixes and cleanups for ext4 this merge window. Of note are 2021-11-10 17:05:37 -08:00
f2fs Update to zstd-1.4.10 2021-11-13 15:32:30 -08:00
fat for-5.16/inode-sync-2021-10-29 2021-11-01 10:25:27 -07:00
freevxfs
fscache fscache: Remove an unused static variable 2021-10-04 22:13:12 +01:00
fuse fuse: release pipe buf after last use 2021-11-25 14:05:18 +01:00
gfs2 gfs2: Prevent endless loops in gfs2_file_buffered_write 2021-11-10 18:22:37 +01:00
hfs Merge branch 'akpm' (patches from Andrew) 2021-11-09 10:11:53 -08:00
hfsplus Merge branch 'akpm' (patches from Andrew) 2021-11-09 10:11:53 -08:00
hostfs hostfs: support splice_write 2021-08-26 22:28:02 +02:00
hpfs treewide: Replace open-coded flex arrays in unions 2021-10-18 12:28:53 -07:00
hugetlbfs mm,hugetlb: remove mlock ulimit for SHM_HUGETLB 2021-11-09 10:02:48 -08:00
iomap iomap: iomap_read_inline_data cleanup 2021-11-24 10:15:47 -08:00
isofs isofs: Fix out of bound access for corrupted isofs image 2021-10-19 12:51:02 +02:00
jbd2 jbd2: add sparse annotations for add_transaction_credits() 2021-08-30 23:36:50 -04:00
jffs2 vfs: add rcu argument to ->get_acl() callback 2021-08-18 22:08:24 +02:00
jfs Just one JFS patch 2021-11-03 09:23:25 -07:00
kernfs Merge 5.15-rc6 into driver-core-next 2021-10-18 09:43:37 +02:00
ksmbd ksmbd: fix memleak in get_file_stream_info() 2021-11-25 00:09:26 -06:00
lockd A slow cycle for nfsd: mainly cleanup, including Neil's patch dropping 2021-11-10 16:45:54 -08:00
minix mm: require ->set_page_dirty to be explicitly wired up 2021-06-29 10:53:48 -07:00
netfs netfs: Adjust docs after foliation 2021-11-29 10:10:26 -08:00
nfs NFS client bugfixes for Linux 5.16 2021-11-27 10:33:55 -08:00
nfs_common nfs: Fix kerneldoc warning shown up by W=1 2021-10-04 22:02:17 +01:00
nfsd This is just one bugfix for a bufferflow in knfsd's xdr decoding. 2021-11-17 08:38:00 -08:00
nilfs2 Merge branch 'akpm' (patches from Andrew) 2021-11-09 10:11:53 -08:00
nls
notify fanotify: Allow users to request FAN_FS_ERROR events 2021-10-27 12:53:45 +02:00
ntfs fs: ntfs: Limit NTFS_RW to page sizes smaller than 64k 2021-11-27 14:34:41 -08:00
ntfs3 gfs2: Fix mmap + page fault deadlocks 2021-11-02 12:25:03 -07:00
ocfs2 Merge branch 'exit-cleanups-for-v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2021-11-10 16:15:54 -08:00
omfs mm: require ->set_page_dirty to be explicitly wired up 2021-06-29 10:53:48 -07:00
openpromfs
orangefs orangefs: three fixes from other folks... 2021-11-09 10:34:06 -08:00
overlayfs overlayfs update for 5.16 2021-11-09 10:51:12 -08:00
proc proc/vmcore: fix clearing user buffer by properly using clear_user() 2021-11-20 10:35:55 -08:00
pstore pstore/blk: Use "%lu" to format unsigned long 2021-11-21 09:44:19 -08:00
qnx4 qnx4: work around gcc false positive warning bug 2021-09-21 08:36:48 -07:00
qnx6
quota \n 2021-11-06 16:40:48 -07:00
ramfs Merge branch 'akpm' (patches from Andrew) 2021-11-09 10:11:53 -08:00
reiserfs \n 2021-11-06 16:40:48 -07:00
romfs
smbfs_common cifs: Move SMB2_Create definitions to the shared area 2021-11-05 09:55:36 -05:00
squashfs lib: zstd: Add kernel-specific API 2021-11-08 16:55:21 -08:00
sysfs fs/sysfs/dir.c: replace S_IRWXU|S_IRUGO|S_IXUGO with 0755 sysfs_create_dir_ns() 2021-10-05 16:35:05 +02:00
sysv sysv: use BUILD_BUG_ON instead of runtime check 2021-11-09 10:02:52 -08:00
tracefs tracefs: Have tracefs directories not set OTH permission bits by default 2021-10-08 18:08:43 -04:00
ubifs fscrypt: remove fscrypt_operations::max_namelen 2021-09-20 19:32:33 -07:00
udf udf: Fix crash after seekdir 2021-11-09 12:53:58 +01:00
ufs isystem: ship and use stdarg.h 2021-08-19 09:02:55 +09:00
unicode .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
vboxsf vboxfs: fix broken legacy mount signature checking 2021-09-27 11:26:21 -07:00
verity fs-verity: fix signed integer overflow with i_size near S64_MAX 2021-09-22 10:56:34 -07:00
xfs xfs: remove xfs_inew_wait 2021-11-24 10:06:02 -08:00
zonefs gfs2: Fix mmap + page fault deadlocks 2021-11-02 12:25:03 -07:00
aio.c Various hardening fixes and cleanups for 5.16-rc1 2021-11-01 17:29:10 -07:00
anon_inodes.c fs: add anon_inode_getfile_secure() similar to anon_inode_getfd_secure() 2021-09-19 22:35:37 -04:00
attr.c fs: handle circular mappings correctly 2021-11-17 09:26:09 +01:00
bad_inode.c vfs: add rcu argument to ->get_acl() callback 2021-08-18 22:08:24 +02:00
binfmt_aout.c binfmt: a.out: Fix bogus semicolon 2021-09-05 10:15:05 -07:00
binfmt_elf_fdpic.c coredump: Limit coredumps to a single thread group 2021-10-08 12:06:02 -05:00
binfmt_elf.c Merge branch 'akpm' (patches from Andrew) 2021-11-09 10:11:53 -08:00
binfmt_flat.c binfmt: remove in-tree usage of MAP_EXECUTABLE 2021-06-29 10:53:50 -07:00
binfmt_misc.c
binfmt_script.c
buffer.c fs: simplify init_page_buffers 2021-10-18 14:43:22 -06:00
char_dev.c
compat_binfmt_elf.c
coredump.c coredump: Limit coredumps to a single thread group 2021-10-08 12:06:02 -05:00
d_path.c d_path: fix Kernel doc validator complaining 2021-11-06 13:30:32 -07:00
dax.c New code for 5.15: 2021-08-31 11:13:35 -07:00
dcache.c useful constants: struct qstr for ".." 2021-04-15 22:36:45 -04:00
direct-io.c fs: get rid of the res2 iocb->ki_complete argument 2021-10-25 10:36:24 -06:00
drop_caches.c fs: drop_caches: fix skipping over shadow cache inodes 2021-09-03 09:58:10 -07:00
eventfd.c eventfd: Export eventfd_wake_count to modules 2021-09-06 07:20:56 -04:00
eventpoll.c ARM development updates for 5.15: 2021-09-09 13:25:49 -07:00
exec.c Merge branch 'exit-cleanups-for-v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2021-11-10 16:15:54 -08:00
fcntl.c Merge branch 'akpm' (patches from Andrew) 2021-09-03 10:08:28 -07:00
fhandle.c switch file_open_root() to struct path 2021-04-07 13:56:43 -04:00
file_table.c
file.c fget: check that the fd still exists after getting a ref to it 2021-12-03 10:06:58 -08:00
filesystems.c fs: simplify get_filesystem_list / get_all_fs_names 2021-08-23 01:25:40 -04:00
fs_context.c memcg: charge fs_context and legacy_fs_context 2021-09-03 09:58:12 -07:00
fs_parser.c namei: Standardize callers of filename_lookup() 2021-09-07 16:07:47 -04:00
fs_pin.c
fs_struct.c
fs_types.c
fs-writeback.c Various hardening fixes and cleanups for 5.16-rc1 2021-11-01 17:29:10 -07:00
fsopen.c
init.c
inode.c fs: Remove FS_THP_SUPPORT 2021-11-17 10:36:35 -05:00
internal.h Merge branch 'akpm' (patches from Andrew) 2021-11-09 10:11:53 -08:00
io_uring.c io_uring: Fix undefined-behaviour in io_issue_sqe 2021-11-27 06:41:38 -07:00
io-wq.c io-wq: serialize hash clear with wakeup 2021-11-11 17:39:46 -07:00
io-wq.h io_uring: optimise INIT_WQ_LIST 2021-10-19 05:49:54 -06:00
ioctl.c New code for 5.15: 2021-08-31 11:06:32 -07:00
Kconfig 4 cifs/smb3 fixes, one for DFS reconnect, and one to begin creating common headers for server and client and the other two to rename the cifs_common directory to smbfs_common to be more consistent ie change use of the name cifs to smb which is more accurate 2021-09-12 10:10:21 -07:00
Kconfig.binfmt binfmt: remove support for em86 (alpha only) 2021-07-25 22:33:03 -07:00
kernel_read_file.c vfs: check fd has read access in kernel_read_file_from_fd() 2021-10-18 20:22:03 -10:00
libfs.c libfs: Support RENAME_EXCHANGE in simple_rename() 2021-11-03 15:43:08 +01:00
locks.c locks: remove changelog comments 2021-10-19 14:11:39 -04:00
Makefile 4 cifs/smb3 fixes, one for DFS reconnect, and one to begin creating common headers for server and client and the other two to rename the cifs_common directory to smbfs_common to be more consistent ie change use of the name cifs to smb which is more accurate 2021-09-12 10:10:21 -07:00
mbcache.c
mount.h
mpage.c
namei.c File locking changes for v5.16 2021-11-01 09:06:53 -07:00
namespace.c Merge branch 'akpm' (patches from Andrew) 2021-09-03 10:08:28 -07:00
no-block.c
nsfs.c
open.c Merge branch 'akpm' (patches from Andrew) 2021-11-06 14:08:17 -07:00
pipe.c Revert "mm/gup: remove try_get_page(), call try_get_compound_head() directly" 2021-09-07 11:03:45 -07:00
pnode.c
pnode.h
posix_acl.c fs/posix_acl.c: avoid -Wempty-body warning 2021-11-06 13:30:32 -07:00
proc_namespace.c
read_write.c fs: remove leftover comments from mandatory locking removal 2021-10-26 12:20:50 -04:00
readdir.c readdir: make sure to verify directory entry for legacy interfaces too 2021-04-17 11:39:49 -07:00
remap_range.c fs: remove mandatory file locking support 2021-08-23 06:15:36 -04:00
select.c Revert "memcg: enable accounting for pollfd and select bits arrays" 2021-09-07 11:26:23 -07:00
seq_file.c seq_file: move seq_escape() to a header 2021-11-09 10:02:52 -08:00
signalfd.c signal: Rename SIL_PERF_EVENT SIL_FAULT_PERF_EVENT for consistency 2021-07-23 13:16:43 -05:00
splice.c
stack.c
stat.c fs: add generic helper for filling statx attribute flags 2021-08-17 11:47:43 +02:00
statfs.c
super.c fs: explicitly unregister per-superblock BDIs 2021-11-06 13:30:34 -07:00
sync.c block: simplify the block device syncing code 2021-10-22 08:36:55 -06:00
timerfd.c timerfd: Provide timerfd_resume() 2021-08-10 17:57:22 +02:00
userfaultfd.c userfaultfd: fix a race between writeprotect and exit_mmap() 2021-10-18 20:22:02 -10:00
utimes.c
xattr.c