From: David Carlier Date: Fri, 17 Apr 2026 05:54:08 +0000 (+0100) Subject: gtp: disable BH before calling udp_tunnel_xmit_skb() X-Git-Tag: v7.1-rc1~36^2~45 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=5638504a2aa9e1b9d72af9060df1a160cce2d379;p=thirdparty%2Fkernel%2Fstable.git gtp: disable BH before calling udp_tunnel_xmit_skb() gtp_genl_send_echo_req() runs as a generic netlink doit handler in process context with BH not disabled. It calls udp_tunnel_xmit_skb(), which eventually invokes iptunnel_xmit() — that uses __this_cpu_inc/dec on softnet_data.xmit.recursion to track the tunnel xmit recursion level. Without local_bh_disable(), the task may migrate between dev_xmit_recursion_inc() and dev_xmit_recursion_dec(), breaking the per-CPU counter pairing. The result is stale or negative recursion levels that can later produce false-positive SKB_DROP_REASON_RECURSION_LIMIT drops on either CPU. The other udp_tunnel_xmit_skb() call sites in gtp.c are unaffected: the data path runs under ndo_start_xmit and the echo response handlers run from the UDP encap rx softirq, both with BH already disabled. Fix it by disabling BH around the udp_tunnel_xmit_skb() call, mirroring commit 2cd7e6971fc2 ("sctp: disable BH before calling udp_tunnel_xmit_skb()"). Fixes: 6f1a9140ecda ("net: add xmit recursion limit to tunnel xmit functions") Cc: stable@vger.kernel.org Signed-off-by: David Carlier Link: https://patch.msgid.link/20260417055408.4667-1-devnexen@gmail.com Signed-off-by: Jakub Kicinski --- diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c index 70b9e58b9b781..5150f2e4f66be 100644 --- a/drivers/net/gtp.c +++ b/drivers/net/gtp.c @@ -2400,6 +2400,7 @@ static int gtp_genl_send_echo_req(struct sk_buff *skb, struct genl_info *info) return -ENODEV; } + local_bh_disable(); udp_tunnel_xmit_skb(rt, sk, skb_to_send, fl4.saddr, fl4.daddr, inet_dscp_to_dsfield(fl4.flowi4_dscp), @@ -2409,6 +2410,7 @@ static int gtp_genl_send_echo_req(struct sk_buff *skb, struct genl_info *info) !net_eq(sock_net(sk), dev_net(gtp->dev)), false, 0); + local_bh_enable(); return 0; }