From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 EDE2B470117; Tue, 25 Aug 2026 13:53:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787666015; cv=none; b=SwCr9O2b1SQMIQ7neWnXmw1yoZs6mrGPRCvOl9aZfT0Nowcr7BFP9w2A3nH4NnkoqVybQWI766JR2F0NSC9MhRtGtPKHC9iNawZ2GLk3/BSdCkh1ixau0T/284Qajyk0lozIRj6ZpGm2RGgyTvzY2P5rUkhM3ON67+4lkwAsTCo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787666015; c=relaxed/simple; bh=FZgUjzyVkjVJed+rFJN1qb0qbQIA0X5eEHr2qXIfmQw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=QPxizeegVVtmU6/KOHuCXC5SCCswh0tNpwg01wxYhGrbctBuwCzO6m2UTi+VgrpMgoPTyBcWy87EePQw0zoZXcgAJlF7akP5cRUOQMRaKtwNm3mLtheGaOnbKu9ox0wCWwGu39Sp1KnvDQSRHG//Nodx//WoppV84Y3pF1YktOM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=gDdrSVJE; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="gDdrSVJE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 564A31F000E9; Tue, 25 Aug 2026 13:53:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1787666013; bh=DxyoXUjUC00KVmjRG6B4kHzDO9u3nHc7FeBDcNXjrFM=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=gDdrSVJEBhnegmH+HBHlcHDc4CVLnnCYdOB7Dx2NUw2h3BbaGyLMjCGV1y8HqkaAZ yh9Qg5eDoVAL0m2YHMKT651HNXJlkBHgVi7mOvLYhOub9PuoPho9wq+yFKAZ7erZhm hNTwiJuDrKIzW9ZroSpCTgyJVewfl20MFpksem08= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Vega , Luxiao Xu , Ren Wei , Vadim Fedorenko , Ido Schimmel , Jakub Kicinski Subject: [PATCH 6.1 56/79] ipv6: fix use-after-free in ip6_finish_output2() Date: Tue, 25 Aug 2026 15:26:36 +0200 Message-ID: <20260825132543.894348816@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260825132541.677185791@linuxfoundation.org> References: <20260825132541.677185791@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Luxiao Xu commit d0d48d999b0eee6bb176ef4e39d9be868fa80f7e upstream. ip6_finish_output2() caches a pointer to the IPv6 destination address (daddr) before invoking lwtunnel_xmit(). The LWT-BPF transmit path or other encapsulation operations within lwtunnel_xmit() can reallocate the skb head, freeing the memory that daddr points to. When lwtunnel_xmit() returns LWTUNNEL_XMIT_CONTINUE, the function continues to use the stale daddr pointer to compute the nexthop and to look up or create the neighbour entry. This results in a use-after-free read, which can leak sensitive kernel data, pollute the neighbour table with arbitrary values, misdirect traffic, or crash the system. Fix this by re-fetching the IPv6 header and the destination address pointer after lwtunnel_xmit() returns LWTUNNEL_XMIT_CONTINUE, ensuring that the subsequent nexthop computation and neighbour lookup operate on valid memory. Fixes: e415ed3a4b8b ("ipv6: use skb_expand_head in ip6_finish_output2") Cc: stable@vger.kernel.org Reported-by: Vega Signed-off-by: Luxiao Xu Signed-off-by: Ren Wei Reviewed-by: Vadim Fedorenko Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/4aa3f53bc44e79572c6dd2340ec7b68ef1a3d87d.1786516730.git.rakukuip@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/ipv6/ip6_output.c | 2 ++ 1 file changed, 2 insertions(+) --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -118,6 +118,8 @@ static int ip6_finish_output2(struct net if (res != LWTUNNEL_XMIT_CONTINUE) return res; + hdr = ipv6_hdr(skb); + daddr = &hdr->daddr; } rcu_read_lock();