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 DD62B41C2E4; Wed, 4 Feb 2026 14:55:20 +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=1770216920; cv=none; b=WyEz1al4/i5HzrkibbHq1Kawoahwb5gfLb1mMFXQ7pXyPkZmQLDSdLQwlcizgHfyqj2QzDiaJORugw4cvTIaRn4AqCuU6Yqs/O9kB7Lu7jzuXtB2CtGI+SnCV3i7wXeijgBV71hmMN+DQtdjE0+nLBHDOLIfOIVG4gr7vN7T0A4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770216920; c=relaxed/simple; bh=KlgOEaccsPzsfrYdofs0Pgmfk7dfN8YGRlmJvVVg9jE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=SSk5S4EngRsWvYLusWx8Yx8riUGjEvXvEvDChtLhC8j/kNPcQ6b5ufkAT/Go479OjPZN92kYq5h37fsZVknBQzhl9HCcHXEoKDnK/udpGGYKR6faMHrBRk0FCeoUquQOYZrlQfm5a8lVexWmaV8m5fq8wlYu4Hd5ije1P25W0f0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=eD1Vg9zs; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="eD1Vg9zs" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 64F21C19423; Wed, 4 Feb 2026 14:55:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1770216920; bh=KlgOEaccsPzsfrYdofs0Pgmfk7dfN8YGRlmJvVVg9jE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=eD1Vg9zszpZlE8C9KloDIgt+vSEFvtuewvu5FbeITGoJO9oF808aqtybMY7LS58OB m5SrKX/o429GuNvNHsD8ancJ3/3/2G5gOSpJnh24bNjd32n6clo3hmaIoEoOI6PkSK eEaljVtmK5NUgbmdK9Lh2uiV5u1J/VQHp4KJ8fhk= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+4d8c7d16b0e95c0d0f0d@syzkaller.appspotmail.com, Kuniyuki Iwashima , Eric Dumazet , Jakub Kicinski , Sasha Levin Subject: [PATCH 5.15 072/206] gue: Fix skb memleak with inner IP protocol 0. Date: Wed, 4 Feb 2026 15:38:23 +0100 Message-ID: <20260204143900.807469735@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260204143858.193781818@linuxfoundation.org> References: <20260204143858.193781818@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Kuniyuki Iwashima [ Upstream commit 9a56796ad258786d3624eef5aefba394fc9bdded ] syzbot reported skb memleak below. [0] The repro generated a GUE packet with its inner protocol 0. gue_udp_recv() returns -guehdr->proto_ctype for "resubmit" in ip_protocol_deliver_rcu(), but this only works with non-zero protocol number. Let's drop such packets. Note that 0 is a valid number (IPv6 Hop-by-Hop Option). I think it is not practical to encap HOPOPT in GUE, so once someone starts to complain, we could pass down a resubmit flag pointer to distinguish two zeros from the upper layer: * no error * resubmit HOPOPT [0] BUG: memory leak unreferenced object 0xffff888109695a00 (size 240): comm "syz.0.17", pid 6088, jiffies 4294943096 hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 40 c2 10 81 88 ff ff 00 00 00 00 00 00 00 00 .@.............. backtrace (crc a84b336f): kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline] slab_post_alloc_hook mm/slub.c:4958 [inline] slab_alloc_node mm/slub.c:5263 [inline] kmem_cache_alloc_noprof+0x3b4/0x590 mm/slub.c:5270 __build_skb+0x23/0x60 net/core/skbuff.c:474 build_skb+0x20/0x190 net/core/skbuff.c:490 __tun_build_skb drivers/net/tun.c:1541 [inline] tun_build_skb+0x4a1/0xa40 drivers/net/tun.c:1636 tun_get_user+0xc12/0x2030 drivers/net/tun.c:1770 tun_chr_write_iter+0x71/0x120 drivers/net/tun.c:1999 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x45d/0x710 fs/read_write.c:686 ksys_write+0xa7/0x170 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xa4/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Fixes: 37dd0247797b1 ("gue: Receive side for Generic UDP Encapsulation") Reported-by: syzbot+4d8c7d16b0e95c0d0f0d@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/6965534b.050a0220.38aacd.0001.GAE@google.com/ Signed-off-by: Kuniyuki Iwashima Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20260115172533.693652-2-kuniyu@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/ipv4/fou.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/ipv4/fou.c b/net/ipv4/fou.c index b1a8e4eec3f6e..e63aa6b52460c 100644 --- a/net/ipv4/fou.c +++ b/net/ipv4/fou.c @@ -213,6 +213,9 @@ static int gue_udp_recv(struct sock *sk, struct sk_buff *skb) return gue_control_message(skb, guehdr); proto_ctype = guehdr->proto_ctype; + if (unlikely(!proto_ctype)) + goto drop; + __skb_pull(skb, sizeof(struct udphdr) + hdrlen); skb_reset_transport_header(skb); -- 2.51.0