From: Linus Torvalds <[email protected]> [ 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 <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Jens Axboe <[email protected]> Signed-off-by: Sasha Levin <[email protected]> --- 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, -- 2.11.0
