Subject: FAILED: patch "[PATCH] pfcp: fix socket lifetime on netdevice registration failure" failed to apply to 6.18-stable tree
To: luoxuanqiang@kylinos.cn,horms@kernel.org,pabeni@redhat.com
Cc: <stable@vger.kernel.org>
From: <gregkh@linuxfoundation.org>
Date: Sat, 03 Oct 2026 15:18:24 +0200
Message-ID: <2026100324-detector-remember-9bba@gregkh>
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The patch below does not apply to the 6.18-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-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x 0f17d2e3dd9cda3ee6d94033d5e5489af168920d
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026100324-detector-remember-9bba@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:


thanks,

greg k-h

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

From 0f17d2e3dd9cda3ee6d94033d5e5489af168920d Mon Sep 17 00:00:00 2001
From: Xuanqiang Luo <luoxuanqiang@kylinos.cn>
Date: Thu, 24 Sep 2026 13:52:52 +0800
Subject: [PATCH] pfcp: fix socket lifetime on netdevice registration failure

pfcp_newlink() creates the UDP socket before register_netdevice().
If registration fails after pfcp_dev_init() succeeds, the core calls
pfcp_dev_uninit(), which releases the socket and clears pfcp->sk.
The newlink error path then releases it again, causing a NULL pointer
dereference. This was observed with failslab fault injection:

  FAULT_INJECTION: forcing a failure.
  kobject: kobject_add_internal failed for pfcp0 (error: -12 parent: net)
  BUG: KASAN: null-ptr-deref in udp_tunnel_sock_release+0x1c/0x50
  Read of size 8 at addr 0000000000000120 by task ip/1037
  Call trace:
   show_stack+0x18/0x24 (C)
   dump_stack_lvl+0x78/0x90
   print_report+0x468/0x5cc
   kasan_report+0xa4/0xf0
   __asan_load8+0x7c/0xd0
   udp_tunnel_sock_release+0x1c/0x50
   pfcp_newlink+0x128/0x184
   rtnl_newlink+0x848/0xe44
   rtnetlink_rcv_msg+0x468/0x514
   netlink_rcv_skb+0xc0/0x1f0
   rtnetlink_rcv+0x18/0x24
   netlink_unicast+0x4b8/0x558
   netlink_sendmsg+0x2b8/0x584
   ...

Return from pfcp_del_sock() if pfcp->sk is NULL.

Fixes: 76c8764ef36a5 ("pfcp: add PFCP module")
Cc: stable@vger.kernel.org
Signed-off-by: Xuanqiang Luo <luoxuanqiang@kylinos.cn>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20260924055252.33488-1-xuanqiang.luo@linux.dev
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/drivers/net/pfcp.c b/drivers/net/pfcp.c
index e1cca779d2ec..3ecd43cafdf0 100644
--- a/drivers/net/pfcp.c
+++ b/drivers/net/pfcp.c
@@ -105,6 +105,9 @@ static int pfcp_encap_recv(struct sock *sk, struct sk_buff *skb)
 
 static void pfcp_del_sock(struct pfcp_dev *pfcp)
 {
+	if (!pfcp->sk)
+		return;
+
 	udp_tunnel_sock_release(pfcp->sk);
 	pfcp->sk = NULL;
 }