This is a note to let you know that I've just added the patch titled
loop: fix concurrent lo_open/lo_release
to the 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
loop-fix-concurrent-lo_open-lo_release.patch
and it can be found in the queue-3.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From ae6650163c66a7eff1acd6eb8b0f752dcfa8eba5 Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
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
From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
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 <long7573@xxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Cc: Ben Hutchings <ben.hutchings@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/block/loop.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
--- 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,
Patches currently in stable-queue which might be from torvalds@xxxxxxxxxxxxxxxxxxxx are
queue-3.18/loop-fix-concurrent-lo_open-lo_release.patch