From ae6650163c66a7eff1acd6eb8b0f752dcfa8eba5 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Fri, 5 Jan 2018 16:26:00 -0800 Subject: loop: fix concurrent lo_open/lo_release MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 --- 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 bc8e61506968..d5fe720cf149 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -1581,9 +1581,8 @@ 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; 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, -- cgit v1.2.3-58-ga151