From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AH8x225CP32favTPKrm5cDcm4rxXDZwFq18S1tPj63BviA3lUssllS+qQRjJNFQTydFJT+H/x/lP ARC-Seal: i=1; a=rsa-sha256; t=1517256598; cv=none; d=google.com; s=arc-20160816; b=nl+XTzFRMdlLV7B05ahQb6MrMs5GB6LwPveC2btZDsHBdnKu38483jyRDB5QvyoQrh i+JGNdpu0IdMMjEqlI+40Qgqa4IhE/S9KPdsg9veF9mgGvEIj1zDT3osYwgwttQVazH6 ODFBp1VtBC0aXlmlWT6W+d77lKaxXFRvee6ZiTfM9erec69xzo1pGqZLVzxaNyOwwp+h s/q8QjSxlZ0IMP2npa9Laq9bRLA38X24po/2CzSLr6+1IbHZ3pymuTpoW8devPmC8sK8 s9OKysT90rOR/GdLiG0kb4Yl0B3OTWbEsNd+W6YDMdweTgqqDM0fR/QqoHeLzNdz3gQA PutA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:in-reply-to:message-id:date :subject:cc:to:from:arc-authentication-results; bh=igpogHY9ffD6tmmJa6tTe49CODb3VdHhDIJdQ7e3swA=; b=XD605Q5J7ck0J5/u0ZbDObHDdvGJY+Mq3YM2UBiye+j19XQzs9+n7qwa5Zuz9VLxli 3WJdzKjHLCthK1HZnA0QIL5zGaH/qoC42eVF0sOI46qzYBGcSfoHVWRnEk20g1WlX0d3 FL32y2I5I5ykA0uUT/aOpE9CAYNusr7jlxo4+us3aMw+HFTRxEAuishHlkChBokiBTMf uz6q/E/mU6nj5hsOolVDaYZzrDX7LO/E31OsccQNdbDiZIGVQhH7E9rXCxGgyPJ8O5LO 68eDqSWiIgq04ixwIdgwVjkWWcIVMPEaWJqxMhlrZ8qBv9aOX/wIS0LCE66Tk2ohEsSS 5LXw== ARC-Authentication-Results: i=1; mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.71.90 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.71.90 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot , Mike Maloney , Eric Dumazet , "David S. Miller" Subject: [PATCH 3.18 51/52] ipv6: fix udpv6 sendmsg crash caused by too small MTU Date: Mon, 29 Jan 2018 13:57:09 +0100 Message-Id: <20180129123630.403883391@linuxfoundation.org> X-Mailer: git-send-email 2.16.1 In-Reply-To: <20180129123628.168904217@linuxfoundation.org> References: <20180129123628.168904217@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcU2VudCI=?= X-GMAIL-THRID: =?utf-8?q?1590958513642109340?= X-GMAIL-MSGID: =?utf-8?q?1590958855087352069?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mike Maloney [ Upstream commit 749439bfac6e1a2932c582e2699f91d329658196 ] The logic in __ip6_append_data() assumes that the MTU is at least large enough for the headers. A device's MTU may be adjusted after being added while sendmsg() is processing data, resulting in __ip6_append_data() seeing any MTU. For an mtu smaller than the size of the fragmentation header, the math results in a negative 'maxfraglen', which causes problems when refragmenting any previous skb in the skb_write_queue, leaving it possibly malformed. Instead sendmsg returns EINVAL when the mtu is calculated to be less than IPV6_MIN_MTU. Found by syzkaller: kernel BUG at ./include/linux/skbuff.h:2064! invalid opcode: 0000 [#1] SMP KASAN Dumping ftrace buffer: (ftrace buffer empty) Modules linked in: CPU: 1 PID: 14216 Comm: syz-executor5 Not tainted 4.13.0-rc4+ #2 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 task: ffff8801d0b68580 task.stack: ffff8801ac6b8000 RIP: 0010:__skb_pull include/linux/skbuff.h:2064 [inline] RIP: 0010:__ip6_make_skb+0x18cf/0x1f70 net/ipv6/ip6_output.c:1617 RSP: 0018:ffff8801ac6bf570 EFLAGS: 00010216 RAX: 0000000000010000 RBX: 0000000000000028 RCX: ffffc90003cce000 RDX: 00000000000001b8 RSI: ffffffff839df06f RDI: ffff8801d9478ca0 RBP: ffff8801ac6bf780 R08: ffff8801cc3f1dbc R09: 0000000000000000 R10: ffff8801ac6bf7a0 R11: 43cb4b7b1948a9e7 R12: ffff8801cc3f1dc8 R13: ffff8801cc3f1d40 R14: 0000000000001036 R15: dffffc0000000000 FS: 00007f43d740c700(0000) GS:ffff8801dc100000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f7834984000 CR3: 00000001d79b9000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: ip6_finish_skb include/net/ipv6.h:911 [inline] udp_v6_push_pending_frames+0x255/0x390 net/ipv6/udp.c:1093 udpv6_sendmsg+0x280d/0x31a0 net/ipv6/udp.c:1363 inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:762 sock_sendmsg_nosec net/socket.c:633 [inline] sock_sendmsg+0xca/0x110 net/socket.c:643 SYSC_sendto+0x352/0x5a0 net/socket.c:1750 SyS_sendto+0x40/0x50 net/socket.c:1718 entry_SYSCALL_64_fastpath+0x1f/0xbe RIP: 0033:0x4512e9 RSP: 002b:00007f43d740bc08 EFLAGS: 00000216 ORIG_RAX: 000000000000002c RAX: ffffffffffffffda RBX: 00000000007180a8 RCX: 00000000004512e9 RDX: 000000000000002e RSI: 0000000020d08000 RDI: 0000000000000005 RBP: 0000000000000086 R08: 00000000209c1000 R09: 000000000000001c R10: 0000000000040800 R11: 0000000000000216 R12: 00000000004b9c69 R13: 00000000ffffffff R14: 0000000000000005 R15: 00000000202c2000 Code: 9e 01 fe e9 c5 e8 ff ff e8 7f 9e 01 fe e9 4a ea ff ff 48 89 f7 e8 52 9e 01 fe e9 aa eb ff ff e8 a8 b6 cf fd 0f 0b e8 a1 b6 cf fd <0f> 0b 49 8d 45 78 4d 8d 45 7c 48 89 85 78 fe ff ff 49 8d 85 ba RIP: __skb_pull include/linux/skbuff.h:2064 [inline] RSP: ffff8801ac6bf570 RIP: __ip6_make_skb+0x18cf/0x1f70 net/ipv6/ip6_output.c:1617 RSP: ffff8801ac6bf570 Reported-by: syzbot Signed-off-by: Mike Maloney Reviewed-by: Eric Dumazet Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv6/ip6_output.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -1214,14 +1214,16 @@ int ip6_append_data(struct sock *sk, int np->cork.tclass = tclass; if (rt->dst.flags & DST_XFRM_TUNNEL) mtu = np->pmtudisc >= IPV6_PMTUDISC_PROBE ? - rt->dst.dev->mtu : dst_mtu(&rt->dst); + READ_ONCE(rt->dst.dev->mtu) : dst_mtu(&rt->dst); else mtu = np->pmtudisc >= IPV6_PMTUDISC_PROBE ? - rt->dst.dev->mtu : dst_mtu(rt->dst.path); + READ_ONCE(rt->dst.dev->mtu) : dst_mtu(rt->dst.path); if (np->frag_size < mtu) { if (np->frag_size) mtu = np->frag_size; } + if (mtu < IPV6_MIN_MTU) + return -EINVAL; cork->fragsize = mtu; if (dst_allfrag(rt->dst.path)) cork->flags |= IPCORK_ALLFRAG;