netdev - Re: [PATCH net] netlink: Fix nlmsg_parse as a wrapper for strict message parsing

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Message-ID: <20190813204300.1d5abc20@cakuba.netronome.com>
Date:   Tue, 13 Aug 2019 20:43:00 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     David Ahern <dsahern@...nel.org>
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        johannes.berg@...el.com, edumazet@...gle.com,
        David Ahern <dsahern@...il.com>
Subject: Re: [PATCH net] netlink: Fix nlmsg_parse as a wrapper for strict
 message parsing

On Mon, 12 Aug 2019 13:07:07 -0700, David Ahern wrote:
> From: David Ahern <dsahern@...il.com>
> 
> Eric reported a syzbot warning:
> 
> BUG: KMSAN: uninit-value in nh_valid_get_del_req+0x6f1/0x8c0 net/ipv4/nexthop.c:1510
> CPU: 0 PID: 11812 Comm: syz-executor444 Not tainted 5.3.0-rc3+ #17
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x191/0x1f0 lib/dump_stack.c:113
>  kmsan_report+0x162/0x2d0 mm/kmsan/kmsan_report.c:109
>  __msan_warning+0x75/0xe0 mm/kmsan/kmsan_instr.c:294
>  nh_valid_get_del_req+0x6f1/0x8c0 net/ipv4/nexthop.c:1510
>  rtm_del_nexthop+0x1b1/0x610 net/ipv4/nexthop.c:1543
>  rtnetlink_rcv_msg+0x115a/0x1580 net/core/rtnetlink.c:5223
>  netlink_rcv_skb+0x431/0x620 net/netlink/af_netlink.c:2477
>  rtnetlink_rcv+0x50/0x60 net/core/rtnetlink.c:5241
>  netlink_unicast_kernel net/netlink/af_netlink.c:1302 [inline]
>  netlink_unicast+0xf6c/0x1050 net/netlink/af_netlink.c:1328
>  netlink_sendmsg+0x110f/0x1330 net/netlink/af_netlink.c:1917
>  sock_sendmsg_nosec net/socket.c:637 [inline]
>  sock_sendmsg net/socket.c:657 [inline]
>  ___sys_sendmsg+0x14ff/0x1590 net/socket.c:2311
>  __sys_sendmmsg+0x53a/0xae0 net/socket.c:2413
>  __do_sys_sendmmsg net/socket.c:2442 [inline]
>  __se_sys_sendmmsg+0xbd/0xe0 net/socket.c:2439
>  __x64_sys_sendmmsg+0x56/0x70 net/socket.c:2439
>  do_syscall_64+0xbc/0xf0 arch/x86/entry/common.c:297
>  entry_SYSCALL_64_after_hwframe+0x63/0xe7
> 
> The root cause is nlmsg_parse calling __nla_parse which means the
> header struct size is not checked.
> 
> nlmsg_parse should be a wrapper around __nlmsg_parse with
> NL_VALIDATE_STRICT for the validate argument very much like
> nlmsg_parse_deprecated is for NL_VALIDATE_LIBERAL.
> 
> Fixes: 3de6440354465 ("netlink: re-add parse/validate functions in strict mode")
> Reported-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Signed-off-by: David Ahern <dsahern@...il.com>

Applied, thank you!