Message ID | 20180129161611.11275-3-kleber.souza@canonical.com |
---|---|
State | New |
Headers | show |
Series | [SRU,X,A,B,1/1] loop: fix concurrent lo_open/lo_release | expand |
On Mon, Jan 29, 2018 at 05:16:11PM +0100, Kleber Sacilotto de Souza wrote: > From: Linus Torvalds <torvalds@linux-foundation.org> > > CVE-2018-5344 > > 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> > (cherry picked from commit ae6650163c66a7eff1acd6eb8b0f752dcfa8eba5) > Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com> Applied to bionic/master-next, thanks!
diff --git a/drivers/block/loop.c b/drivers/block/loop.c index bc8e61506968..d5fe720cf149 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -1581,9 +1581,8 @@ static int lo_open(struct block_device *bdev, fmode_t mode) return err; } -static void lo_release(struct gendisk *disk, fmode_t mode) +static void __lo_release(struct loop_device *lo) { - struct loop_device *lo = disk->private_data; int err; if (atomic_dec_return(&lo->lo_refcnt)) @@ -1610,6 +1609,13 @@ static void lo_release(struct gendisk *disk, fmode_t mode) mutex_unlock(&lo->lo_ctl_mutex); } +static void lo_release(struct gendisk *disk, fmode_t mode) +{ + mutex_lock(&loop_index_mutex); + __lo_release(disk->private_data); + mutex_unlock(&loop_index_mutex); +} + static const struct block_device_operations lo_fops = { .owner = THIS_MODULE, .open = lo_open,