From: Linus Torvalds torvalds@linux-foundation.org
This patch has been added to the 4.1 stable tree. If you have any objections, please let us know.
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[ 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 ea0c863861b9..b5dbce192c6b 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -1338,9 +1338,8 @@ 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;
mutex_lock(&lo->lo_ctl_mutex); @@ -1368,6 +1367,13 @@ 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,