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Nicholas Bellinger 0ad134d81c configfs: Fix race between create_link and configfs_rmdir 
commit ba80aa909c99802c428682c352b0ee0baac0acd3 upstream.

This patch closes a long standing race in configfs between
the creation of a new symlink in create_link(), while the
symlink target's config_item is being concurrently removed
via configfs_rmdir().

This can happen because the symlink target's reference
is obtained by config_item_get() in create_link() before
the CONFIGFS_USET_DROPPING bit set by configfs_detach_prep()
during configfs_rmdir() shutdown is actually checked..

This originally manifested itself on ppc64 on v4.8.y under
heavy load using ibmvscsi target ports with Novalink API:

[ 7877.289863] rpadlpar_io: slot U8247.22L.212A91A-V1-C8 added
[ 7879.893760] ------------[ cut here ]------------
[ 7879.893768] WARNING: CPU: 15 PID: 17585 at ./include/linux/kref.h:46 config_item_get+0x7c/0x90 [configfs]
[ 7879.893811] CPU: 15 PID: 17585 Comm: targetcli Tainted: G           O 4.8.17-customv2.22 #12
[ 7879.893812] task: c00000018a0d3400 task.stack: c0000001f3b40000
[ 7879.893813] NIP: d000000002c664ec LR: d000000002c60980 CTR: c000000000b70870
[ 7879.893814] REGS: c0000001f3b43810 TRAP: 0700   Tainted: G O     (4.8.17-customv2.22)
[ 7879.893815] MSR: 8000000000029033 <SF,EE,ME,IR,DR,RI,LE>  CR: 28222242  XER: 00000000
[ 7879.893820] CFAR: d000000002c664bc SOFTE: 1
                GPR00: d000000002c60980 c0000001f3b43a90 d000000002c70908 c0000000fbc06820
                GPR04: c0000001ef1bd900 0000000000000004 0000000000000001 0000000000000000
                GPR08: 0000000000000000 0000000000000001 d000000002c69560 d000000002c66d80
                GPR12: c000000000b70870 c00000000e798700 c0000001f3b43ca0 c0000001d4949d40
                GPR16: c00000014637e1c0 0000000000000000 0000000000000000 c0000000f2392940
                GPR20: c0000001f3b43b98 0000000000000041 0000000000600000 0000000000000000
                GPR24: fffffffffffff000 0000000000000000 d000000002c60be0 c0000001f1dac490
                GPR28: 0000000000000004 0000000000000000 c0000001ef1bd900 c0000000f2392940
[ 7879.893839] NIP [d000000002c664ec] config_item_get+0x7c/0x90 [configfs]
[ 7879.893841] LR [d000000002c60980] check_perm+0x80/0x2e0 [configfs]
[ 7879.893842] Call Trace:
[ 7879.893844] [c0000001f3b43ac0] [d000000002c60980] check_perm+0x80/0x2e0 [configfs]
[ 7879.893847] [c0000001f3b43b10] [c000000000329770] do_dentry_open+0x2c0/0x460
[ 7879.893849] [c0000001f3b43b70] [c000000000344480] path_openat+0x210/0x1490
[ 7879.893851] [c0000001f3b43c80] [c00000000034708c] do_filp_open+0xfc/0x170
[ 7879.893853] [c0000001f3b43db0] [c00000000032b5bc] do_sys_open+0x1cc/0x390
[ 7879.893856] [c0000001f3b43e30] [c000000000009584] system_call+0x38/0xec
[ 7879.893856] Instruction dump:
[ 7879.893858] 409d0014 38210030 e8010010 7c0803a6 4e800020 3d220000 e94981e0 892a0000
[ 7879.893861] 2f890000 409effe0 39200001 992a0000 <0fe00000> 4bffffd0 60000000 60000000
[ 7879.893866] ---[ end trace 14078f0b3b5ad0aa ]---

To close this race, go ahead and obtain the symlink's target
config_item reference only after the existing CONFIGFS_USET_DROPPING
check succeeds.

This way, if configfs_rmdir() wins create_link() will return -ENONET,
and if create_link() wins configfs_rmdir() will return -EBUSY.

Reported-by: Bryant G. Ly <bryantly@linux.vnet.ibm.com>
Tested-by: Bryant G. Ly <bryantly@linux.vnet.ibm.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-06-26 07:13:08 +02:00
..
9p
9p: fix a potential acl leak
2017-05-14 13:32:54 +02:00
adfs
…
affs
affs: fix remount failure when there are no options changed
2016-06-07 18:14:32 -07:00
afs
…
autofs4
autofs: use dentry flags to block walks during expire
2016-09-30 10:18:37 +02:00
befs
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
2015-07-04 19:36:06 -07:00
bfs
…
btrfs
btrfs: fix memory leak in update_space_info failure path
2017-06-14 13:16:24 +02:00
cachefiles
FS-Cache: Add missing initialization of ret in cachefiles_write_page()
2015-11-16 20:38:43 -05:00
ceph
fs: add i_blocksize()
2017-06-14 13:16:24 +02:00
cifs
Call echo service immediately after socket reconnect
2017-06-17 06:39:35 +02:00
coda
fs/coda: fix readlink buffer overflow
2015-09-10 13:29:01 -07:00
configfs
configfs: Fix race between create_link and configfs_rmdir
2017-06-26 07:13:08 +02:00
cramfs
…
debugfs
debugfs: Make automount point inodes permanently empty
2016-05-04 14:48:41 -07:00
devpts
devpts: clean up interface to pty drivers
2016-08-16 09:30:49 +02:00
dlm
dlm: free workqueues after the connections
2016-10-22 12:26:56 +02:00
ecryptfs
ecryptfs: fix handling of directory opening
2016-09-15 08:27:47 +02:00
efivarfs
efi: Make efivarfs entries immutable by default
2016-03-03 15:07:09 -08:00
efs
…
exofs
osd fs: __r4w_get_page rely on PageUptodate for uptodate
2015-12-12 10:15:34 -08:00
exportfs
…
ext2
posix_acl: Clear SGID bit when setting file permissions
2016-10-31 04:13:58 -06:00
ext4
fs: add i_blocksize()
2017-06-14 13:16:24 +02:00
f2fs
fscrypt: avoid collisions when presenting long encrypted filenames
2017-05-25 14:30:11 +02:00
fat
fat: fix using uninitialized fields of fat_inode/fsinfo_inode
2017-03-15 09:57:15 +08:00
freevxfs
freevxfs: Grammar s/an negative/a negative/
2015-08-07 13:59:24 +02:00
fscache
FS-Cache: Initialise stores_lock in netfs cookie
2017-06-17 06:39:37 +02:00
fuse
fuse: add missing FR_FORCE
2017-03-12 06:37:28 +01:00
gfs2
gfs2: avoid uninitialized variable warning
2017-04-30 05:49:28 +02:00
hfs
hfs: fix B-tree corruption after insertion at position 0
2015-09-10 13:29:01 -07:00
hfsplus
posix_acl: Clear SGID bit when setting file permissions
2016-10-31 04:13:58 -06:00
hostfs
hostfs: Freeing an ERR_PTR in hostfs_fill_sb_common()
2016-09-30 10:18:39 +02:00
hpfs
hpfs: implement the show_options method
2016-06-01 12:15:54 -07:00
hugetlbfs
fs/hugetlbfs/inode.c: fix bugs in hugetlb_vmtruncate_list()
2016-02-25 12:01:22 -08:00
isofs
isofs: Do not return EACCES for unknown filesystems
2016-10-28 03:01:34 -04:00
jbd2
jbd2: don't leak modified metadata buffers on an aborted journal
2017-03-12 06:37:26 +01:00
jffs2
posix_acl: Clear SGID bit when setting file permissions
2016-10-31 04:13:58 -06:00
jfs
fs: add i_blocksize()
2017-06-14 13:16:24 +02:00
kernfs
kernfs: don't depend on d_find_any_alias() when generating notifications
2016-09-24 10:07:36 +02:00
lockd
Mainly smaller bugfixes and cleanup. We're still finding some bugs from
2015-11-11 20:11:28 -08:00
logfs
mm, fs: introduce mapping_gfp_constraint()
2015-11-06 17:50:42 -08:00
minix
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
2015-07-04 19:36:06 -07:00
ncpfs
ncpfs: fix a braino in OOM handling in ncp_fill_cache()
2016-03-16 08:42:59 -07:00
nfs
nfs: Fix "Don't increment lock sequence ID after NFS4ERR_MOVED"
2017-06-17 06:39:38 +02:00
nfs_common
lockd: NLM grace period shouldn't block NFSv4 opens
2015-08-13 10:22:06 -04:00
nfsd
fs: add i_blocksize()
2017-06-14 13:16:24 +02:00
nilfs2
fs: add i_blocksize()
2017-06-14 13:16:24 +02:00
nls
…
notify
fanotify: fix list corruption in fanotify_get_response()
2016-09-30 10:18:37 +02:00
ntfs
mm, fs: introduce mapping_gfp_constraint()
2015-11-06 17:50:42 -08:00
ocfs2
fs: add i_blocksize()
2017-06-14 13:16:24 +02:00
omfs
…
openpromfs
…
overlayfs
ovl: fsync after copy-up
2016-11-10 16:36:34 +01:00
proc
proc: add a schedule point in proc_pid_readdir()
2017-06-17 06:39:38 +02:00
pstore
pstore/ram: Use memcpy_fromio() to save old buffer
2016-10-28 03:01:27 -04:00
qnx4
…
qnx6
…
quota
quota: Fix possible GPF due to uninitialised pointers
2016-04-12 09:08:56 -07:00
ramfs
mm, fs: obey gfp_mapping for add_to_page_cache()
2015-10-16 11:42:28 -07:00
reiserfs
fs: add i_blocksize()
2017-06-14 13:16:24 +02:00
romfs
romfs: use different way to generate fsid for BLOCK or MTD
2017-06-17 06:39:38 +02:00
squashfs
squashfs: xattr simplifications
2015-11-13 20:34:33 -05:00
sysfs
sysfs: be careful of error returns from ops->show()
2017-04-12 12:38:33 +02:00
sysv
fix sysvfs symlinks
2015-11-23 21:11:08 -05:00
tracefs
tracefs: Fix refcount imbalance in start_creating()
2015-11-04 22:13:45 -05:00
ubifs
ubifs: Fix journal replay wrt. xattr nodes
2017-01-26 08:23:48 +01:00
udf
fs: add i_blocksize()
2017-06-14 13:16:24 +02:00
ufs
ufs_getfrag_block(): we only grab ->truncate_mutex on block creation path
2017-06-14 13:16:24 +02:00
xfs
Make __xfs_xattr_put_listen preperly report errors.
2017-06-14 13:16:27 +02:00
aio.c
aio: mark AIO pseudo-fs noexec
2016-10-07 15:23:47 +02:00
anon_inodes.c
…
attr.c
vfs: move permission checking into notify_change() for utimes(NULL)
2016-10-22 12:26:56 +02:00
bad_inode.c
…
binfmt_aout.c
…
binfmt_elf_fdpic.c
libnvdimm for 4.4:
2015-11-10 12:07:22 -08:00
binfmt_elf.c
Merge branch 'for-linus-2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
2015-11-11 09:45:24 -08:00
binfmt_em86.c
…
binfmt_flat.c
…
binfmt_misc.c
…
binfmt_script.c
…
block_dev.c
fs/block_dev: always invalidate cleancache in invalidate_bdev()
2017-05-20 14:27:01 +02:00
buffer.c
fs: add i_blocksize()
2017-06-14 13:16:24 +02:00
char_dev.c
fs/char_dev.c: fix incorrect documentation for unregister_chrdev_region
2015-08-05 13:49:35 -07:00
compat_binfmt_elf.c
…
compat_ioctl.c
i2c-dev: Fix typo in ioctl name reference
2015-10-23 23:26:43 +02:00
compat.c
…
coredump.c
coredump: fix unfreezable coredumping task
2016-11-18 10:48:34 +01:00
dax.c
dax: disable pmd mappings
2015-11-16 23:54:45 -08:00
dcache.c
mnt: Protect the mountpoint hashtable with mount_lock
2017-01-19 20:17:21 +01:00
dcookies.c
…
direct-io.c
fs: add i_blocksize()
2017-06-14 13:16:24 +02:00
drop_caches.c
inode: convert inode_sb_list_lock to per-sb
2015-08-17 18:39:46 -04:00
eventfd.c
…
eventpoll.c
…
exec.c
exec: Ensure mm->user_ns contains the execed files
2017-01-06 11:16:14 +01:00
fcntl.c
…
fhandle.c
fs/coredump: prevent fsuid=0 dumps into user-controlled directories
2016-04-12 09:08:58 -07:00
file_table.c
fs, file table: reinit files_stat.max_files after deferred memory initialisation
2015-08-07 04:39:40 +03:00
file.c
vfs: clear remainder of 'full_fds_bits' in dup_fd()
2015-11-05 23:05:32 -08:00
filesystems.c
…
fs_pin.c
…
fs_struct.c
…
fs-writeback.c
writeback, cgroup: fix use of the wrong bdi_writeback which mismatches the inode
2016-04-12 09:09:04 -07:00
inode.c
vfs: fix deadlock in file_remove_privs() on overlayfs
2016-08-10 11:49:30 +02:00
internal.h
inode: rename i_wb_list to i_io_list
2015-08-17 23:38:10 -04:00
ioctl.c
…
Kconfig
dax: disable pmd mappings
2015-11-16 23:54:45 -08:00
Kconfig.binfmt
…
libfs.c
fs: Set the size of empty dirs to 0.
2015-08-12 15:28:45 -05:00
locks.c
locks: use file_inode()
2016-08-10 11:49:27 +02:00
Makefile
ext4: promote ext4 over ext2 in the default probe order
2015-10-15 10:33:21 -04:00
mbcache.c
…
mount.h
mnt: Add a per mount namespace limit on the number of mounts
2017-04-30 05:49:28 +02:00
mpage.c
fs: add i_blocksize()
2017-06-14 13:16:24 +02:00
namei.c
fs: Check for invalid i_uid in may_follow_link()
2016-09-15 08:27:49 +02:00
namespace.c
mnt: Add a per mount namespace limit on the number of mounts
2017-04-30 05:49:28 +02:00
no-block.c
…
nsfs.c
fs/seq_file: convert int seq_vprint/seq_printf/etc... returns to void
2015-09-11 15:21:34 -07:00
open.c
vfs: add vfs_select_inode() helper
2016-05-18 17:06:48 -07:00
pipe.c
pipe: limit the per-user amount of pages allocated in pipes
2016-06-07 18:14:35 -07:00
pnode.c
mnt: Add a per mount namespace limit on the number of mounts
2017-04-30 05:49:28 +02:00
pnode.h
mnt: Add a per mount namespace limit on the number of mounts
2017-04-30 05:49:28 +02:00
posix_acl.c
tmpfs: clear S_ISGID when setting posix ACLs
2017-01-26 08:23:47 +01:00
proc_namespace.c
vfs: show_vfsstat: do not ignore errors from show_devname method
2016-04-12 09:08:55 -07:00
read_write.c
…
readdir.c
…
select.c
…
seq_file.c
fs/seq_file: fix out-of-bounds read
2016-09-07 08:32:43 +02:00
signalfd.c
signalfd: fix information leak in signalfd_copyinfo
2015-08-07 04:39:40 +03:00
splice.c
vfs: fix uninitialized flags in splice_to_pipe()
2017-02-23 17:43:09 +01:00
stack.c
…
stat.c
ufs: restore maintaining ->i_blocks
2017-06-14 13:16:24 +02:00
statfs.c
…
super.c
fs/super.c: fix race between freeze_super() and thaw_super()
2016-10-28 03:01:32 -04:00
sync.c
fs/sync.c: make sync_file_range(2) use WB_SYNC_NONE writeback
2015-11-06 17:50:42 -08:00
timerfd.c
timerfd: Protect the might cancel mechanism proper
2017-05-08 07:46:01 +02:00
userfaultfd.c
userfaultfd: don't block on the last VM updates at exit time
2016-03-16 08:43:01 -07:00
utimes.c
vfs: move permission checking into notify_change() for utimes(NULL)
2016-10-22 12:26:56 +02:00
xattr.c
fs/xattr.c: zero out memory copied to userspace in getxattr
2017-05-20 14:27:01 +02:00