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 897F73C1FCC; Thu, 15 Jan 2026 17:29:55 +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=1768498195; cv=none; b=RpFKJ+Bj09a6PD/Ldxkz78e2zjm80PMf2pYqSfNyRD6j+qgHAVN1tjTxIC8bL6YIcYXGKPZ5+ro3xOM3P+V3/ejcDPxS5cgCkNMxUpTOwgaNcNPgEeJSZ/HCyxSsUTSbWp63Nwa+i1f845UGVQ2mPrMzP/hp+xr0qufG8ZggtTY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768498195; c=relaxed/simple; bh=+C6Oict6VGh7RElSrcnZiXzvTn53zGYz1NL/i1hXqHQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=SIkMPMx/a8kjm/r4lqoz05akFfVTWiQEGf8YkHLjJRsPrKb9y2s6bM8RwgfM+ZtPbSPpSTDd07xUBlVX8PB2p8dPAFNOtlEaeK3aA6zHTV0vtFxp1AZujBmagRfqIB2dLSOvnVtXjRRr60tezcFOOCqYHNJq5mIwGcykVuInDSY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=j+Fds1V9; 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="j+Fds1V9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CC293C116D0; Thu, 15 Jan 2026 17:29:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1768498195; bh=+C6Oict6VGh7RElSrcnZiXzvTn53zGYz1NL/i1hXqHQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=j+Fds1V9R1OSc1OCWFiFK1SUTV82hhizLqku0MqB3tqQCnm/47of4a+wYXIHBdEdm G426VR0mxMMvcu1gMjiNbYlMvWhnPN88y9jPvZH0yMW0rXA0o0q89Vk5rz/AAxqw32 cpzpOyYTKeuXTL6SseurSJP95fH6qh8EPkxt1ldQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+43a2ebcf2a64b1102d64@syzkaller.appspotmail.com, Eric Dumazet , Paolo Abeni , Sasha Levin Subject: [PATCH 5.15 345/554] ip6_gre: make ip6gre_header() robust Date: Thu, 15 Jan 2026 17:46:51 +0100 Message-ID: <20260115164258.716815348@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260115164246.225995385@linuxfoundation.org> References: <20260115164246.225995385@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: Eric Dumazet [ Upstream commit db5b4e39c4e63700c68a7e65fc4e1f1375273476 ] Over the years, syzbot found many ways to crash the kernel in ip6gre_header() [1]. This involves team or bonding drivers ability to dynamically change their dev->needed_headroom and/or dev->hard_header_len In this particular crash mld_newpack() allocated an skb with a too small reserve/headroom, and by the time mld_sendpack() was called, syzbot managed to attach an ip6gre device. [1] skbuff: skb_under_panic: text:ffffffff8a1d69a8 len:136 put:40 head:ffff888059bc7000 data:ffff888059bc6fe8 tail:0x70 end:0x6c0 dev:team0 ------------[ cut here ]------------ kernel BUG at net/core/skbuff.c:213 ! skb_under_panic net/core/skbuff.c:223 [inline] skb_push+0xc3/0xe0 net/core/skbuff.c:2641 ip6gre_header+0xc8/0x790 net/ipv6/ip6_gre.c:1371 dev_hard_header include/linux/netdevice.h:3436 [inline] neigh_connected_output+0x286/0x460 net/core/neighbour.c:1618 neigh_output include/net/neighbour.h:556 [inline] ip6_finish_output2+0xfb3/0x1480 net/ipv6/ip6_output.c:136 __ip6_finish_output net/ipv6/ip6_output.c:-1 [inline] ip6_finish_output+0x234/0x7d0 net/ipv6/ip6_output.c:220 NF_HOOK_COND include/linux/netfilter.h:307 [inline] ip6_output+0x340/0x550 net/ipv6/ip6_output.c:247 NF_HOOK+0x9e/0x380 include/linux/netfilter.h:318 mld_sendpack+0x8d4/0xe60 net/ipv6/mcast.c:1855 mld_send_cr net/ipv6/mcast.c:2154 [inline] mld_ifc_work+0x83e/0xd60 net/ipv6/mcast.c:2693 Fixes: c12b395a4664 ("gre: Support GRE over IPv6") Reported-by: syzbot+43a2ebcf2a64b1102d64@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/693b002c.a70a0220.33cd7b.0033.GAE@google.com/T/#u Signed-off-by: Eric Dumazet Link: https://patch.msgid.link/20251211173550.2032674-1-edumazet@google.com Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin --- net/ipv6/ip6_gre.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c index 501630e3f1b6..84ba9ad00135 100644 --- a/net/ipv6/ip6_gre.c +++ b/net/ipv6/ip6_gre.c @@ -1383,9 +1383,16 @@ static int ip6gre_header(struct sk_buff *skb, struct net_device *dev, { struct ip6_tnl *t = netdev_priv(dev); struct ipv6hdr *ipv6h; + int needed; __be16 *p; - ipv6h = skb_push(skb, t->hlen + sizeof(*ipv6h)); + needed = t->hlen + sizeof(*ipv6h); + if (skb_headroom(skb) < needed && + pskb_expand_head(skb, HH_DATA_ALIGN(needed - skb_headroom(skb)), + 0, GFP_ATOMIC)) + return -needed; + + ipv6h = skb_push(skb, needed); ip6_flow_hdr(ipv6h, 0, ip6_make_flowlabel(dev_net(dev), skb, t->fl.u.ip6.flowlabel, true, &t->fl.u.ip6)); -- 2.51.0