From: Linus Torvalds torvalds@linux-foundation.org
[ Upstream commit ae6650163c66a7eff1acd6eb8b0f752dcfa8eba5 ]
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 Signed-off-by: Sasha Levin alexander.levin@microsoft.com --- drivers/block/loop.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 6cb1beb47c25..94385b969f67 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -1512,9 +1512,8 @@ out: 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;
mutex_lock(&lo->lo_ctl_mutex); @@ -1542,6 +1541,13 @@ out: 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,