This is a note to let you know that I've just added the patch titled
9p/xen : Fix use after free bug in xen_9pfs_front_remove due to race condition
to the 4.19-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:
9p-xen-fix-use-after-free-bug-in-xen_9pfs_front_remo.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 6024a36d85d41c83a6f98e8ac12c9b51a42a1bda
Author: Zheng Wang <zyytlz.wz@xxxxxxx>
Date: Mon Mar 13 22:43:25 2023 +0800
9p/xen : Fix use after free bug in xen_9pfs_front_remove due to race condition
[ Upstream commit ea4f1009408efb4989a0f139b70fb338e7f687d0 ]
In xen_9pfs_front_probe, it calls xen_9pfs_front_alloc_dataring
to init priv->rings and bound &ring->work with p9_xen_response.
When it calls xen_9pfs_front_event_handler to handle IRQ requests,
it will finally call schedule_work to start the work.
When we call xen_9pfs_front_remove to remove the driver, there
may be a sequence as follows:
Fix it by finishing the work before cleanup in xen_9pfs_front_free.
Note that, this bug is found by static analysis, which might be
false positive.
CPU0 CPU1
|p9_xen_response
xen_9pfs_front_remove|
xen_9pfs_front_free|
kfree(priv) |
//free priv |
|p9_tag_lookup
|//use priv->client
Fixes: 71ebd71921e4 ("xen/9pfs: connect to the backend")
Signed-off-by: Zheng Wang <zyytlz.wz@xxxxxxx>
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@xxxxxxxxxxxxxxx>
Signed-off-by: Eric Van Hensbergen <ericvh@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/9p/trans_xen.c b/net/9p/trans_xen.c
index 08b96aeaff464..c87146a496363 100644
--- a/net/9p/trans_xen.c
+++ b/net/9p/trans_xen.c
@@ -299,6 +299,10 @@ static void xen_9pfs_front_free(struct xen_9pfs_front_priv *priv)
write_unlock(&xen_9pfs_lock);
for (i = 0; i < priv->num_rings; i++) {
+ struct xen_9pfs_dataring *ring = &priv->rings[i];
+
+ cancel_work_sync(&ring->work);
+
if (!priv->rings[i].intf)
break;
if (priv->rings[i].irq > 0)
