From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (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 826691FB25 for ; Wed, 19 Jul 2023 21:09:03 +0000 (UTC) Received: from smtp-fw-2101.amazon.com (smtp-fw-2101.amazon.com [72.21.196.25]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0E26A1BF0 for ; Wed, 19 Jul 2023 14:09:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1689800943; x=1721336943; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=wLNiGM11K2K1HCO2weFDCpExzeMXR5fOBfUbc0RRoV0=; b=oz8B/x0JgQ0+RqPXgnjzFZ0KmRR8v60J/oBAwMwGzZO3DO9b8xAecIgb tgm1kezbH06VOPyeJ9yFR66KvGuEK1BeU3/BjnnWBu1GIW/zY86CWYnKR Qbvu/8xxVCyMeXd5rXK+T2ls+FicuWFpqB2f7EETj5LeAqSaWJoX1F1Jf Q=; X-IronPort-AV: E=Sophos;i="6.01,216,1684800000"; d="scan'208";a="340640634" Received: from iad12-co-svc-p1-lb1-vlan3.amazon.com (HELO email-inbound-relay-pdx-2b-m6i4x-f253a3a3.us-west-2.amazon.com) ([10.43.8.6]) by smtp-border-fw-2101.iad2.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Jul 2023 21:08:59 +0000 Received: from EX19MTAUWA002.ant.amazon.com (pdx1-ws-svc-p6-lb9-vlan3.pdx.amazon.com [10.236.137.198]) by email-inbound-relay-pdx-2b-m6i4x-f253a3a3.us-west-2.amazon.com (Postfix) with ESMTPS id 477098A9A1; Wed, 19 Jul 2023 21:08:57 +0000 (UTC) Received: from EX19D004ANA001.ant.amazon.com (10.37.240.138) by EX19MTAUWA002.ant.amazon.com (10.250.64.202) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.30; Wed, 19 Jul 2023 21:08:53 +0000 Received: from 88665a182662.ant.amazon.com (10.106.101.39) by EX19D004ANA001.ant.amazon.com (10.37.240.138) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1118.30; Wed, 19 Jul 2023 21:08:50 +0000 From: Kuniyuki Iwashima To: CC: , , , , , , , , , , Subject: Re: [PATCH v1 net 2/2] af_packet: Fix warning of fortified memcpy() in packet_getname(). Date: Wed, 19 Jul 2023 14:08:41 -0700 Message-ID: <20230719210841.61515-1-kuniyu@amazon.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20230719185322.44255-3-kuniyu@amazon.com> References: <20230719185322.44255-3-kuniyu@amazon.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.106.101.39] X-ClientProxiedBy: EX19D037UWC001.ant.amazon.com (10.13.139.197) To EX19D004ANA001.ant.amazon.com (10.37.240.138) Precedence: Bulk X-Spam-Status: No, score=-1.7 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, RCVD_IN_DNSWL_BLOCKED,RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL, SPF_HELO_NONE,T_SCC_BODY_TEXT_LINE,T_SPF_PERMERROR autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net From: Kuniyuki Iwashima Date: Wed, 19 Jul 2023 11:53:22 -0700 > syzkaller found a warning in packet_getname() [0], where we try to > copy 16 bytes to sockaddr_ll.sll_addr[8]. > > Some devices (ip6gre, vti6, ip6tnl) have 16 bytes address expressed > by struct in6_addr. > > The write seems to overflow, but actually not since we use struct > sockaddr_storage defined in __sys_getsockname(). > > To avoid the warning, we need to let __fortify_memcpy_chk() know the > actual buffer size. > > Another option would be to use strncpy() and limit the copied length > to sizeof(sll_addr), but it will return the partial address and might > break an application that passes sockaddr_storage to getsockname(). > > [0]: > memcpy: detected field-spanning write (size 16) of single field "sll->sll_addr" at net/packet/af_packet.c:3604 (size 8) > WARNING: CPU: 0 PID: 255 at net/packet/af_packet.c:3604 packet_getname+0x25c/0x3a0 net/packet/af_packet.c:3604 > Modules linked in: > CPU: 0 PID: 255 Comm: syz-executor750 Not tainted 6.5.0-rc1-00330-g60cc1f7d0605 #4 > Hardware name: linux,dummy-virt (DT) > pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) > pc : packet_getname+0x25c/0x3a0 net/packet/af_packet.c:3604 > lr : packet_getname+0x25c/0x3a0 net/packet/af_packet.c:3604 > sp : ffff800089887bc0 > x29: ffff800089887bc0 x28: ffff000010f80f80 x27: 0000000000000003 > x26: dfff800000000000 x25: ffff700011310f80 x24: ffff800087d55000 > x23: dfff800000000000 x22: ffff800089887c2c x21: 0000000000000010 > x20: ffff00000de08310 x19: ffff800089887c20 x18: ffff800086ab1630 > x17: 20646c6569662065 x16: 6c676e697320666f x15: 0000000000000001 > x14: 1fffe0000d56d7ca x13: 0000000000000000 x12: 0000000000000000 > x11: 0000000000000000 x10: 0000000000000000 x9 : 3e60944c3da92b00 > x8 : 3e60944c3da92b00 x7 : 0000000000000001 x6 : 0000000000000001 > x5 : ffff8000898874f8 x4 : ffff800086ac99e0 x3 : ffff8000803f8808 > x2 : 0000000000000001 x1 : 0000000100000000 x0 : 0000000000000000 > Call trace: > packet_getname+0x25c/0x3a0 net/packet/af_packet.c:3604 > __sys_getsockname+0x168/0x24c net/socket.c:2042 > __do_sys_getsockname net/socket.c:2057 [inline] > __se_sys_getsockname net/socket.c:2054 [inline] > __arm64_sys_getsockname+0x7c/0x94 net/socket.c:2054 > __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] > invoke_syscall+0x98/0x2c0 arch/arm64/kernel/syscall.c:52 > el0_svc_common+0x134/0x240 arch/arm64/kernel/syscall.c:139 > do_el0_svc+0x64/0x198 arch/arm64/kernel/syscall.c:188 > el0_svc+0x2c/0x7c arch/arm64/kernel/entry-common.c:647 > el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:665 > el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:591 > > Fixes: df8fc4e934c1 ("kbuild: Enable -fstrict-flex-arrays=3") > Reported-by: syzkaller > Signed-off-by: Kuniyuki Iwashima > --- > net/packet/af_packet.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c > index 85ff90a03b0c..5eef94a32a4f 100644 > --- a/net/packet/af_packet.c > +++ b/net/packet/af_packet.c > @@ -3601,7 +3601,10 @@ static int packet_getname(struct socket *sock, struct sockaddr *uaddr, > if (dev) { > sll->sll_hatype = dev->type; > sll->sll_halen = dev->addr_len; > - memcpy(sll->sll_addr, dev->dev_addr, dev->addr_len); > + > + /* Let __fortify_memcpy_chk() know the actual buffer size. */ > + memcpy(((struct sockaddr_storage *)sll)->__data + > + offsetof(struct sockaddr_ll, sll_addr), dev->dev_addr, dev->addr_len); Sorry, this offset was wrong and needs minus offsetof(struct sockaddr_ll, sll_family). Will fix in v2. pw-bot: cr > } else { > sll->sll_hatype = 0; /* Bad: we have no ARPHRD_UNSPEC */ > sll->sll_halen = 0; > -- > 2.30.2