From: Linus Torvalds Date: Sat, 6 Jan 2018 00:26:00 +0000 (-0800) Subject: loop: fix concurrent lo_open/lo_release X-Git-Tag: v3.18.94~33 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=524a6efbd1234439ba00176006ed95ad7d007da6;p=thirdparty%2Fkernel%2Fstable.git loop: fix concurrent lo_open/lo_release commit ae6650163c66a7eff1acd6eb8b0f752dcfa8eba5 upstream. 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 Signed-off-by: Linus Torvalds Signed-off-by: Jens Axboe Cc: Ben Hutchings Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 6cb1beb47c25d..94385b969f675 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,