From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 92754DDCD for ; Sat, 9 May 2026 14:21:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778336518; cv=none; b=Zm39znhiW1HilLBcswdEREdlCmd4l3kjM+DAwPhwDNpXeK5HtT+duN/bptPCrRSHl2qnUQEmeFJmLRB1IVDfSNNJ+NSkgDYoGAO12XyiddolDllPFdrqkqUuGXcAfmApRN6Z5GpbJbOlCA+52kgIZIBGb04ofd7UKBc8GgOEcnQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778336518; c=relaxed/simple; bh=pLOPgvP8/md3i61/Iy1kMcHOo9DQefk7H1SNISo92Zc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=utz1G2ruXzkqwjqBzpvdvRJtG4fkKWILfmPMNpmUtI+8tQ07xbfVqpYra6ACwbjwlQFvRbN4a4MqIYw2Ow4adnx3lcaQKbMwGTjPpx97lAtBt9zi1RxIod9NkJEcPYwhpltrlUgMth05l7p6k32vSVO9fzIChygLygI6zsVr8Ic= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Zjh3neru; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Zjh3neru" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D38AEC2BCB2; Sat, 9 May 2026 14:21:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778336518; bh=pLOPgvP8/md3i61/Iy1kMcHOo9DQefk7H1SNISo92Zc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Zjh3neruxZ3w3OKodTrXwT41WtNP9Uao3Zy5X9qg0Ut4bvYOo7rGOe3VOh3F1L488 WSwumXGNXLLbqXf8p65Dax3wjwhSDsvgVUyqDBwSi5Nt2OR4D0bcGY8+gosysv3ZWl kuJfmFBjxaidkTbLHj3fLwXwC3otIXz8V8kjS1yIRiqJ7qi+t22belGe4a0Q4SaW6R 1KMmz3tXiH3LkoDaMvVtCwdUS34dTsZECmNrIV6EKfNqcuChV0KGUk9wNDaZfWDF+j vn8ADbIw31cCu82SGTBHPNOvJmSEXgKqc/i2bskvnVnHjlmpU5G+BazHpn9S6zt2rO eWzJAhHtlkSXA== From: Sasha Levin To: stable@vger.kernel.org Cc: David Carlier , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.12.y] gtp: disable BH before calling udp_tunnel_xmit_skb() Date: Sat, 9 May 2026 10:21:55 -0400 Message-ID: <20260509142155.3462128-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026050428-flaky-polish-d0e3@gregkh> References: <2026050428-flaky-polish-d0e3@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: David Carlier [ Upstream commit 5638504a2aa9e1b9d72af9060df1a160cce2d379 ] 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 [ Context ] Signed-off-by: Sasha Levin --- drivers/net/gtp.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c index 33b78b4007fe7..d7f644dfaa8d9 100644 --- a/drivers/net/gtp.c +++ b/drivers/net/gtp.c @@ -2401,6 +2401,7 @@ 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, fl4.flowi4_tos, @@ -2410,6 +2411,7 @@ 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); + local_bh_enable(); return 0; } -- 2.53.0