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NeilBrown bcc7f5b4be block_dev: don't test bdev->bd_contains when it is not stable 
bdev->bd_contains is not stable before calling __blkdev_get().
When __blkdev_get() is called on a parition with ->bd_openers == 0
it sets
  bdev->bd_contains = bdev;
which is not correct for a partition.
After a call to __blkdev_get() succeeds, ->bd_openers will be > 0
and then ->bd_contains is stable.

When FMODE_EXCL is used, blkdev_get() calls
   bd_start_claiming() ->  bd_prepare_to_claim() -> bd_may_claim()

This call happens before __blkdev_get() is called, so ->bd_contains
is not stable.  So bd_may_claim() cannot safely use ->bd_contains.
It currently tries to use it, and this can lead to a BUG_ON().

This happens when a whole device is already open with a bd_holder (in
use by dm in my particular example) and two threads race to open a
partition of that device for the first time, one opening with O_EXCL and
one without.

The thread that doesn't use O_EXCL gets through blkdev_get() to
__blkdev_get(), gains the ->bd_mutex, and sets bdev->bd_contains = bdev;

Immediately thereafter the other thread, using FMODE_EXCL, calls
bd_start_claiming() from blkdev_get().  This should fail because the
whole device has a holder, but because bdev->bd_contains == bdev
bd_may_claim() incorrectly reports success.
This thread continues and blocks on bd_mutex.

The first thread then sets bdev->bd_contains correctly and drops the mutex.
The thread using FMODE_EXCL then continues and when it calls bd_may_claim()
again in:
			BUG_ON(!bd_may_claim(bdev, whole, holder));
The BUG_ON fires.

Fix this by removing the dependency on ->bd_contains in
bd_may_claim().  As bd_may_claim() has direct access to the whole
device, it can simply test if the target bdev is the whole device.

Fixes: 6b4517a791 ("block: implement bd_claiming and claiming block")
Cc: stable@vger.kernel.org (v2.6.35+)
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
 		2016-12-13 21:07:08 -07:00
..
9p block,fs: untangle fs.h and blk_types.h 2016-11-01 09:43:26 -06:00
adfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
affs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
afs afs: call->operation_ID sometimes used as __be32 sometimes as u32 2016-10-13 17:03:52 +01:00
autofs4 autofs: refactor ioctl fn vector in iookup_dev_ioctl() 2016-10-11 15:06:31 -07:00
befs befs fixes for 4.9-rc1 2016-10-15 12:09:13 -07:00
bfs Merge remote-tracking branch 'ovl/rename2' into for-linus 2016-10-10 23:02:51 -04:00
btrfs Merge branch 'for-4.10/block' of git://git.kernel.dk/linux-block 2016-12-13 10:19:16 -08:00
cachefiles Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
ceph ceph: don't set req->r_locked_dir in ceph_d_revalidate 2016-12-08 14:32:16 +01:00
cifs Merge branch 'for-4.10/block' of git://git.kernel.dk/linux-block 2016-12-13 10:19:16 -08:00
coda Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
configfs Merge remote-tracking branch 'ovl/rename2' into for-linus 2016-10-10 23:02:51 -04:00
cramfs more trivial ->iterate_shared conversions 2016-05-09 11:41:14 -04:00
crypto fscrypto: don't use on-stack buffer for key derivation 2016-11-19 20:56:13 -05:00
debugfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
devpts Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
dlm genetlink: mark families as __ro_after_init 2016-10-27 16:16:09 -04:00
ecryptfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
efivarfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
efs fs/efs/super.c: fix return value 2016-05-20 17:58:30 -07:00
exofs fs: exofs: print a hex number after a 0x prefix 2016-10-27 18:43:43 -07:00
exportfs exportfs: be careful to only return expected errors. 2016-10-06 09:07:44 -04:00
ext2 ext2: avoid bogus -Wmaybe-uninitialized warning 2016-10-18 11:29:35 +02:00
ext4 Merge branch 'for-4.10/block' of git://git.kernel.dk/linux-block 2016-12-13 10:19:16 -08:00
f2fs Merge branch 'for-4.10/block' of git://git.kernel.dk/linux-block 2016-12-13 10:19:16 -08:00
fat Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
freevxfs freevxfs: update Kconfig information 2016-06-13 10:20:39 +02:00
fscache Merge branch 'd_real' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs into work.misc 2016-06-30 23:34:49 -04:00
fuse fuse: fix clearing suid, sgid for chown() 2016-12-06 16:18:45 +01:00
gfs2 writeback: add wbc_to_write_flags() 2016-11-02 10:24:03 -06:00
hfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
hfsplus block,fs: use REQ_* flags directly 2016-11-01 09:43:26 -06:00
hostfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
hpfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
hugetlbfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
isofs Merge branch 'for-4.10/block' of git://git.kernel.dk/linux-block 2016-12-13 10:19:16 -08:00
jbd2 Merge branch 'for-4.10/block' of git://git.kernel.dk/linux-block 2016-12-13 10:19:16 -08:00
jffs2 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
jfs block,fs: use REQ_* flags directly 2016-11-01 09:43:26 -06:00
kernfs kernfs: Declare two local data structures static 2016-11-29 20:58:31 +01:00
lockd netns: make struct pernet_operations::id unsigned int 2016-11-18 10:59:15 -05:00
logfs fs: logfs: remove unnecesary check 2016-11-22 08:57:55 -07:00
minix Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
ncpfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
nfs Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2016-11-26 23:42:21 -05:00
nfs_common netns: make struct pernet_operations::id unsigned int 2016-11-18 10:59:15 -05:00
nfsd netns: make struct pernet_operations::id unsigned int 2016-11-18 10:59:15 -05:00
nilfs2 block,fs: use REQ_* flags directly 2016-11-01 09:43:26 -06:00
nls
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notify fsnotify: clean up spinlock assertions 2016-10-07 18:46:26 -07:00
ntfs Merge branch 'for-4.10/block' of git://git.kernel.dk/linux-block 2016-12-13 10:19:16 -08:00
ocfs2 Merge branch 'for-4.10/block' of git://git.kernel.dk/linux-block 2016-12-13 10:19:16 -08:00
omfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
openpromfs fs: Replace CURRENT_TIME with current_time() for inode timestamps 2016-09-27 21:06:21 -04:00
orangefs Merge branch 'for-4.10/block' of git://git.kernel.dk/linux-block 2016-12-13 10:19:16 -08:00
overlayfs ovl: fix d_real() for stacked fs 2016-11-29 10:20:24 +01:00
proc xen: features and fixes for 4.10 rc0 2016-12-13 16:07:55 -08:00
pstore Improvements and fixes to pstore subsystem: 2016-12-13 09:16:11 -08:00
qnx4 more trivial ->iterate_shared conversions 2016-05-09 11:41:14 -04:00
qnx6 more trivial ->iterate_shared conversions 2016-05-09 11:41:14 -04:00
quota genetlink: mark families as __ro_after_init 2016-10-27 16:16:09 -04:00
ramfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
reiserfs mm: only include blk_types in swap.h if CONFIG_SWAP is enabled 2016-11-01 09:43:26 -06:00
romfs romfs, squashfs: switch to ->iterate_shared() 2016-05-09 11:41:15 -04:00
squashfs block,fs: untangle fs.h and blk_types.h 2016-11-01 09:43:26 -06:00
sysfs Merge branch 'for-4.9' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2016-10-14 12:18:50 -07:00
sysv Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
tracefs fs: Replace CURRENT_TIME with current_time() for inode timestamps 2016-09-27 21:06:21 -04:00
ubifs ubifs: Fix regression in ubifs_readdir() 2016-10-28 14:48:31 +02:00
udf block,fs: untangle fs.h and blk_types.h 2016-11-01 09:43:26 -06:00
ufs block,fs: untangle fs.h and blk_types.h 2016-11-01 09:43:26 -06:00
xfs Merge branch 'for-4.10/block' of git://git.kernel.dk/linux-block 2016-12-13 10:19:16 -08:00
Kconfig mm/hugetlb: introduce ARCH_HAS_GIGANTIC_PAGE 2016-10-07 18:46:29 -07:00
Kconfig.binfmt docs: fix locations of several documents that got moved 2016-10-24 08:12:35 -02:00
Makefile fs: introduce iomap infrastructure 2016-06-21 09:23:11 +10:00
aio.c aio: fix freeze protection of aio writes 2016-10-30 13:09:42 -04:00
anon_inodes.c
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attr.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
bad_inode.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
binfmt_aout.c fs: fix binfmt_aout.c build error 2016-05-28 16:34:59 -07:00
binfmt_elf.c binfmt_elf: use vmalloc() for allocation of vma_filesz 2016-12-12 18:55:10 -08:00
binfmt_elf_fdpic.c elf_fdpic_transfer_args_to_stack(): make it generic 2016-07-25 16:51:49 +10:00
binfmt_em86.c fs/binfmt_em86.c: fix incompatible pointer type 2016-08-02 19:35:15 -04:00
binfmt_flat.c binfmt_flat: allow compressed flat binary format to work on MMU systems 2016-07-28 13:29:12 +10:00
binfmt_misc.c fs: Replace current_fs_time() with current_time() 2016-09-27 21:06:22 -04:00
binfmt_script.c
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block_dev.c block_dev: don't test bdev->bd_contains when it is not stable 2016-12-13 21:07:08 -07:00
buffer.c Merge branch 'for-4.10/block' of git://git.kernel.dk/linux-block 2016-12-13 10:19:16 -08:00
char_dev.c dax: define a unified inode/address_space for device-dax mappings 2016-08-23 22:58:51 -07:00
compat.c compat: remove compat_printk() 2016-09-27 21:20:53 -04:00
compat_binfmt_elf.c
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compat_ioctl.c fs: compat_ioctl: add pretimeout functions for watchdogs 2016-09-24 09:27:18 +02:00
coredump.c coredump: fix unfreezable coredumping task 2016-11-11 08:12:37 -08:00
dax.c lib: radix-tree: update callback for changing leaf nodes 2016-12-12 18:55:08 -08:00
dcache.c Merge branch 'for-linus-2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-08-07 10:01:14 -04:00
dcookies.c
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direct-io.c block: move poll code to blk-mq 2016-11-11 13:40:25 -07:00
drop_caches.c
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eventfd.c eventfd: document lockless access in eventfd_poll 2016-03-22 15:36:02 -07:00
eventpoll.c fs: poll/select/recvmmsg: use timespec64 for timeout events 2016-05-19 19:12:14 -07:00
exec.c posix-timers: Make them configurable 2016-11-16 09:26:35 +01:00
fcntl.c
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fhandle.c fs/coredump: prevent fsuid=0 dumps into user-controlled directories 2016-03-22 15:36:02 -07:00
file.c fs/file: more unsigned file descriptors 2016-09-27 18:47:38 -04:00
file_table.c
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filesystems.c
…
fs-writeback.c fs/fs-writeback.c: remove redundant if check 2016-12-12 18:55:08 -08:00
fs_pin.c
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fs_struct.c
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inode.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
internal.h Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 13:04:49 -07:00
ioctl.c vfs: cap dedupe request structure size at PAGE_SIZE 2016-09-15 13:29:52 -07:00
iomap.c fs: Do to trim high file position bits in iomap_page_mkwrite_actor 2016-10-24 14:20:25 +11:00
libfs.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
locks.c locking, fs/locks: Add missing file_sem locks 2016-10-18 12:21:28 +02:00
mbcache.c mbcache: fix to detect failure of register_shrinker 2016-08-31 11:44:36 -04:00
mount.h mnt: Add a per mount namespace limit on the number of mounts 2016-09-30 12:46:48 -05:00
mpage.c writeback: add wbc_to_write_flags() 2016-11-02 10:24:03 -06:00
namei.c Merge branch 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs 2016-10-14 17:23:33 -07:00
namespace.c This adds a new gcc plugin named "latent_entropy". It is designed to 2016-10-15 10:03:15 -07:00
no-block.c
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nsfs.c net: add an ioctl to get a socket network namespace 2016-10-31 10:56:36 -04:00
open.c xfs: reflink update for 4.9-rc1 2016-10-13 20:28:22 -07:00
pipe.c pipe: cap initial pipe capacity according to pipe-max-size limit 2016-10-11 15:06:32 -07:00
pnode.c mnt: Add a per mount namespace limit on the number of mounts 2016-09-30 12:46:48 -05:00
pnode.h mnt: Add a per mount namespace limit on the number of mounts 2016-09-30 12:46:48 -05:00
posix_acl.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
proc_namespace.c vfs: show_vfsstat: do not ignore errors from show_devname method 2016-03-16 13:09:08 -04:00
read_write.c iov_iter: kernel-doc import_iovec() and rw_copy_check_uvector() 2016-10-14 20:00:34 -04:00
readdir.c restore killability of old mutex_lock_killable(&inode->i_mutex) users 2016-05-26 00:13:25 -04:00
select.c fs/select: add vmalloc fallback for select(2) 2016-10-11 15:06:30 -07:00
seq_file.c seq/proc: modify seq_put_decimal_[u]ll to take a const char *, not char 2016-10-07 18:46:30 -07:00
signalfd.c
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splice.c Merge branch 'for-4.10/block' of git://git.kernel.dk/linux-block 2016-12-13 10:19:16 -08:00
stack.c
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stat.c
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statfs.c
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super.c fs/super.c: don't fool lockdep in freeze_super() and thaw_super() paths 2016-10-14 20:41:59 -04:00
sync.c mm, fs: get rid of PAGE_CACHE_* and page_cache_{get,release} macros 2016-04-04 10:41:08 -07:00
timerfd.c timerfd: Reject ALARM timerfds without CAP_WAKE_ALARM 2016-06-09 23:42:38 +02:00
userfaultfd.c mm: introduce fault_env 2016-07-26 16:19:19 -07:00
utimes.c Merge remote-tracking branch 'jk/vfs' into work.misc 2016-10-08 11:06:08 -04:00
xattr.c xattr: Fix setting security xattrs on sockfs 2016-11-17 00:00:23 -05:00