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loop: fix concurrent lo_open/lo_release

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范龙飞 reports that KASAN can report a use-after-free in __lock_acquire.
The reason is due to insufficient serialization in lo_release(), which
will continue to use the loop device even after it has decremented the
lo_refcnt to zero.

In the meantime, another process can come in, open the loop device
again as it is being shut down. Confusion ensues.

Reported-by: 范龙飞 <long7573@126.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Git-commit: ae6650163c66a7eff1acd6eb8b0f752dcfa8eba5
Git-repo: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Signed-off-by: Srinivasa Rao Kuppala <srkupp@codeaurora.org>

Conflicts:
	drivers/block/loop.c

Signed-off-by: Dheeraj Kumar Chaudhary <dheech@codeaurora.org>
Change-Id: I965ddcdc2a9d27fd56a54d2886b7c3861c21b05f
CVE-2018-5344
Signed-off-by: Kevin F. Haggerty <haggertk@lineageos.org>
This commit is contained in:
Linus Torvalds 2018-01-05 16:26:00 -08:00 committed by Francescodario Cuzzocrea
parent 9f2375feac
commit bcf18f5455
1 changed files with 10 additions and 2 deletions
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12
drivers/block/loop.c
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@ -1505,9 +1505,8 @@ out:
return err; return err;
} }
static int lo_release(struct gendisk *disk, fmode_t mode) static int __lo_release(struct loop_device *lo)
{ {
struct loop_device *lo = disk->private_data;
int err; int err;
mutex_lock(&lo->lo_ctl_mutex); mutex_lock(&lo->lo_ctl_mutex);
@ -1537,6 +1536,15 @@ out_unlocked:
return 0; return 0;
} }
static int lo_release(struct gendisk *disk, fmode_t mode)
{
int err;
mutex_lock(&loop_index_mutex);
err =__lo_release(disk->private_data);
mutex_unlock(&loop_index_mutex);
return err;
}
static const struct block_device_operations lo_fops = { static const struct block_device_operations lo_fops = {
.owner = THIS_MODULE, .owner = THIS_MODULE,
.open = lo_open, .open = lo_open,