FAILED: patch "[PATCH] net: phonet: free phonet_device after RCU grace period" failed to apply to 5.15-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 5.15-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 <stable@vger.kernel.org>.

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-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 71de0177b28da751f407581a4515cf4d762f6296
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026061547-discourse-faceless-4af5@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

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

From 71de0177b28da751f407581a4515cf4d762f6296 Mon Sep 17 00:00:00 2001
From: Santosh Kalluri <santosh.kalluri129@gmail.com>
Date: Wed, 3 Jun 2026 17:08:43 -0700
Subject: [PATCH] net: phonet: free phonet_device after RCU grace period
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

phonet_device_destroy() removes a phonet_device from the per-net device
list with list_del_rcu(), but frees it immediately. RCU readers walking
the same list can still hold a pointer to the object after it has been
removed, leading to a slab-use-after-free.

Use kfree_rcu(), matching the lifetime rule already used by
phonet_address_del() for the same object type.

Fixes: eeb74a9d45f7 ("Phonet: convert devices list to RCU")
Cc: stable@vger.kernel.org
Signed-off-by: Santosh Kalluri <santosh.kalluri129@gmail.com>
Acked-by: Rémi Denis-Courmont <remi@remlab.net>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/phonet/pn_dev.c b/net/phonet/pn_dev.c
index 86325b7fc1b6..ad44831d6745 100644
--- a/net/phonet/pn_dev.c
+++ b/net/phonet/pn_dev.c
@@ -108,7 +108,7 @@ static void phonet_device_destroy(struct net_device *dev)
 		for_each_set_bit(addr, pnd->addrs, 64)
 			phonet_address_notify(net, RTM_DELADDR, ifindex, addr);
 
-		kfree(pnd);
+		kfree_rcu(pnd, rcu);
 	}
 }