From nobody Mon Jun 8 19:00:26 2026 Received: from azure-sdnproxy.icoremail.net (azure-sdnproxy.icoremail.net [207.46.229.174]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 39E603BB10A; Wed, 27 May 2026 08:18:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=207.46.229.174 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779869929; cv=none; b=LJcBstPyRqu3Ih0rs0pC7K9RF41Gg1A/61bLyGo8DQkNK9bOroqzS/TNTtjHWU5i7RhFpcGp+td6Nx5ZYzIZRxceVr0Df934rgP7pCGG/58Iqje6jxDS6nqmJempENllrPiGeV/fLYK2Ex61yyPvPdn7LzbTLNIzWcl7sgSAMx0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779869929; c=relaxed/simple; bh=syfk5959tJHAPWULL5+nOqHgS2Vt+pN5sQcrmx2+q1w=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=WHKIT5QSQ2c08rz9FPxOZdEVZkOnSnB4ScZFDswvWX7XaXpiV767hXZTkYkEOhFYPoI718TjP49OJfSGcvwNgLTxD6/xnr5SLT7U91OZ36Ywb4XE42aDZArq4/+D908oJaYY5EvwIHt5GVdGD7qkM75kKeqCrUT9cpXi7vFJC9c= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=mails.tsinghua.edu.cn; spf=pass smtp.mailfrom=mails.tsinghua.edu.cn; dkim=pass (1024-bit key) header.d=mails.tsinghua.edu.cn header.i=@mails.tsinghua.edu.cn header.b=QEL+pgSx; arc=none smtp.client-ip=207.46.229.174 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=mails.tsinghua.edu.cn Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=mails.tsinghua.edu.cn Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=mails.tsinghua.edu.cn header.i=@mails.tsinghua.edu.cn header.b="QEL+pgSx" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mails.tsinghua.edu.cn; s=dkim; h=Received:From:To:Cc:Subject: Date:Message-ID:MIME-Version:Content-Transfer-Encoding; bh=2rub8 xVFH79HgKRt47yMxbSOY6mYiviajCZO6Mf7T5k=; b=QEL+pgSxblLp9DWSugux8 gguAPIWCC+lsykNdN3bz1BL63x+vsVOwTjA62HksH9jrMuYD54Yj7Mtut3mH1Pqd wxyrG3bG67SiNfygShp1SRDqdUk7cRJgGmjOCwCwszoDMS0jF+AO5IGOXgRhOHay HQeun4ksVS8WI1vq+BcCjI= Received: from localhost.localdomain (unknown [211.102.241.99]) by web3 (Coremail) with SMTP id ygQGZQA3go_ZqBZqOrztAQ--.39780S2; Wed, 27 May 2026 16:18:33 +0800 (CST) From: Yizhou Zhao To: netdev@vger.kernel.org Cc: Yizhou Zhao , Alexander Aring , "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , linux-bluetooth@vger.kernel.org, linux-wpan@vger.kernel.org, linux-kernel@vger.kernel.org, Yuxiang Yang , Ao Wang , Xuewei Feng , Qi Li , Ke Xu Subject: [PATCH net] 6lowpan: fix off-by-one in multicast context address compression Date: Wed, 27 May 2026 16:18:01 +0800 Message-ID: <20260527081806.42747-1-zhaoyz24@mails.tsinghua.edu.cn> X-Mailer: git-send-email 2.46.2 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: ygQGZQA3go_ZqBZqOrztAQ--.39780S2 X-Coremail-Antispam: 1UD129KBjvJXoW7tw1rtw18tw45WF4UJr4rAFb_yoW8Zry3pa s7A3s0yF97JrW3u392yw1jvw17uF4kJrWay340ya4YvFn0gF10yr18KFWkJas0yrWYk34j qFWUCrWYyan8GrDanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUP014x267AKxVW8JVW5JwAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2ocxC64kIII0Yj41l84x0c7CEw4AK67xGY2AK02 1l84ACjcxK6xIIjxv20xvE14v26w1j6s0DM28EF7xvwVC0I7IYx2IY6xkF7I0E14v26r4U JVWxJr1l84ACjcxK6I8E87Iv67AKxVW0oVCq3wA2z4x0Y4vEx4A2jsIEc7CjxVAFwI0_Gc CE3s1lnxkEFVAIw20F6cxK64vIFxWle2I262IYc4CY6c8Ij28IcVAaY2xG8wAqx4xG64xv F2IEw4CE5I8CrVC2j2WlYx0E2Ix0cI8IcVAFwI0_Jr0_Jr4lYx0Ex4A2jsIE14v26r1j6r 4UMcvjeVCFs4IE7xkEbVWUJVW8JwACjcxG0xvY0x0EwIxGrwACjI8F5VA0II8E6IAqYI8I 648v4I1lFIxGxcIEc7CjxVA2Y2ka0xkIwI1lc7CjxVAaw2AFwI0_Jw0_GFylc2xSY4AK67 AK6r43MxAIw28IcxkI7VAKI48JMxC20s026xCaFVCjc4AY6r1j6r4UMI8I3I0E5I8CrVAF wI0_Jr0_Jr4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE17CEb7AF67AKxVW8ZVWrXwCIc4 0Y0x0EwIxGrwCI42IY6xIIjxv20xvE14v26r1j6r1xMIIF0xvE2Ix0cI8IcVCY1x0267AK xVW8JVWxJwCI42IY6xAIw20EY4v20xvaj40_Jr0_JF4lIxAIcVC2z280aVAFwI0_Jr0_Gr 1lIxAIcVC2z280aVCY1x0267AKxVW8JVW8JrUvcSsGvfC2KfnxnUUI43ZEXa7VUjXTm3UU UUU== X-CM-SenderInfo: 52kd05r2suqzpdlo2hxwvl0wxkxdhvlgxou0/1tbiAQEAAWoWnq0YHQAAsL Content-Type: text/plain; charset="utf-8" The second memcpy in lowpan_iphc_mcast_ctx_addr_compress() uses &data[1] as destination and &ipaddr->s6_addr[11] as source, but both should be offset by one: &data[2] and &ipaddr->s6_addr[12] respectively. This off-by-one has two consequences: 1. data[1] is overwritten with s6_addr[11], corrupting the RIID field in the compressed multicast address 2. data[5] is never written, so uninitialized kernel stack memory is transmitted over the network via lowpan_push_hc_data(), leaking kernel stack contents The correct inline data layout must match what the decompression function lowpan_uncompress_multicast_ctx_daddr() expects: data[0..1] =3D s6_addr[1..2] (flags/scope + RIID) data[2..5] =3D s6_addr[12..15] (group ID) Also zero-initialize the data array as a defensive measure against similar bugs in the future. Fixes: 5609c185f24d ("6lowpan: iphc: add support for stateful compression") Reported-by: Yizhou Zhao Reported-by: Yuxiang Yang Reported-by: Ao Wang Reported-by: Xuewei Feng Reported-by: Qi Li Reported-by: Ke Xu Assisted-by: GLM:GLM-5.1 Signed-off-by: Yizhou Zhao Acked-by: Alexander Aring --- diff --git a/net/6lowpan/iphc.c b/net/6lowpan/iphc.c index e116d30..37eaff3 100644 --- a/net/6lowpan/iphc.c +++ b/net/6lowpan/iphc.c @@ -1086,12 +1086,12 @@ static u8 lowpan_iphc_mcast_ctx_addr_compress(u8 **= hc_ptr, const struct lowpan_iphc_ctx *ctx, const struct in6_addr *ipaddr) { - u8 data[6]; + u8 data[6] =3D {}; =20 /* flags/scope, reserved (RIID) */ memcpy(data, &ipaddr->s6_addr[1], 2); /* group ID */ - memcpy(&data[1], &ipaddr->s6_addr[11], 4); + memcpy(&data[2], &ipaddr->s6_addr[12], 4); lowpan_push_hc_data(hc_ptr, data, 6); =20 return LOWPAN_IPHC_DAM_00; -- 2.43.0