FAILED: patch "[PATCH] xfrm6: fix inet6_dev refcount underflow problem" failed to apply to 6.1-stable tree

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x cc9b364bb1d58d3dae270c7a931a8cc717dc2b3b
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2023102001-barometer-press-265e@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From cc9b364bb1d58d3dae270c7a931a8cc717dc2b3b Mon Sep 17 00:00:00 2001
From: Zhang Changzhong <[email protected]>
Date: Fri, 15 Sep 2023 19:20:41 +0800
Subject: [PATCH] xfrm6: fix inet6_dev refcount underflow problem

There are race conditions that may lead to inet6_dev refcount underflow in xfrm6_dst_destroy() and rt6_uncached_list_flush_dev().

One of the refcount underflow bugs is shown below:

	(cpu 1)                	|	(cpu 2)
xfrm6_dst_destroy()             |
  ...                           |
  in6_dev_put()                 |
				|  rt6_uncached_list_flush_dev()
  ...				|    ...
				|    in6_dev_put()

rt6_uncached_list_del() | ...
... |

xfrm6_dst_destroy() calls rt6_uncached_list_del() after in6_dev_put(), so rt6_uncached_list_flush_dev() has a chance to call in6_dev_put() again for the same inet6_dev.

Fix it by moving in6_dev_put() after rt6_uncached_list_del() in xfrm6_dst_destroy().

index 188224a76685..45d0f9a8b28c 100644
@@ -117,10 +117,10 @@ static void xfrm6_dst_destroy(struct dst_entry *dst)
 {
 	struct xfrm_dst *xdst = (struct xfrm_dst *)dst;
 
-	if (likely(xdst->u.rt6.rt6i_idev))
-		in6_dev_put(xdst->u.rt6.rt6i_idev);
 	dst_destroy_metrics_generic(dst);
 	rt6_uncached_list_del(&xdst->u.rt6);
+	if (likely(xdst->u.rt6.rt6i_idev))
+		in6_dev_put(xdst->u.rt6.rt6i_idev);
 	xfrm_dst_destroy(xdst);
 }