netdev - Re: [PATCH net] ipv6: prevent possible NULL dereference in rt6

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Date: Sun, 16 Jun 2024 08:59:00 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, David Ahern <dsahern@...nel.org>, netdev@...r.kernel.org, 
	eric.dumazet@...il.com
Subject: Re: [PATCH net] ipv6: prevent possible NULL dereference in rt6_probe()

On Sat, Jun 15, 2024 at 11:15 PM Eric Dumazet <edumazet@...gle.com> wrote:
>
> syzbot caught a NULL dereference in rt6_probe() [1]
>
> Bail out if  __in6_dev_get() returns NULL.
>
> [1]
> Oops: general protection fault, probably for non-canonical address 0xdffffc00000000cb: 0000 [#1] PREEMPT SMP KASAN PTI
> KASAN: null-ptr-deref in range [0x0000000000000658-0x000000000000065f]
> CPU: 1 PID: 22444 Comm: syz-executor.0 Not tainted 6.10.0-rc2-syzkaller-00383-gb8481381d4e2 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
>  RIP: 0010:rt6_probe net/ipv6/route.c:656 [inline]
>  RIP: 0010:find_match+0x8c4/0xf50 net/ipv6/route.c:758
> Code: 14 fd f7 48 8b 85 38 ff ff ff 48 c7 45 b0 00 00 00 00 48 8d b8 5c 06 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 19
> RSP: 0018:ffffc900034af070 EFLAGS: 00010203
> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffc90004521000
> RDX: 00000000000000cb RSI: ffffffff8990d0cd RDI: 000000000000065c
> RBP: ffffc900034af150 R08: 0000000000000005 R09: 0000000000000000
> R10: 0000000000000001 R11: 0000000000000002 R12: 000000000000000a
> R13: 1ffff92000695e18 R14: ffff8880244a1d20 R15: 0000000000000000
> FS:  00007f4844a5a6c0(0000) GS:ffff8880b9300000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000001b31b27000 CR3: 000000002d42c000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>   rt6_nh_find_match+0xfa/0x1a0 net/ipv6/route.c:784
>   nexthop_for_each_fib6_nh+0x26d/0x4a0 net/ipv4/nexthop.c:1496
>   __find_rr_leaf+0x6e7/0xe00 net/ipv6/route.c:825
>   find_rr_leaf net/ipv6/route.c:853 [inline]
>   rt6_select net/ipv6/route.c:897 [inline]
>   fib6_table_lookup+0x57e/0xa30 net/ipv6/route.c:2195
>   ip6_pol_route+0x1cd/0x1150 net/ipv6/route.c:2231
>   pol_lookup_func include/net/ip6_fib.h:616 [inline]
>   fib6_rule_lookup+0x386/0x720 net/ipv6/fib6_rules.c:121
>   ip6_route_output_flags_noref net/ipv6/route.c:2639 [inline]
>   ip6_route_output_flags+0x1d0/0x640 net/ipv6/route.c:2651
>   ip6_dst_lookup_tail.constprop.0+0x961/0x1760 net/ipv6/ip6_output.c:1147
>   ip6_dst_lookup_flow+0x99/0x1d0 net/ipv6/ip6_output.c:1250
>   rawv6_sendmsg+0xdab/0x4340 net/ipv6/raw.c:898
>   inet_sendmsg+0x119/0x140 net/ipv4/af_inet.c:853
>   sock_sendmsg_nosec net/socket.c:730 [inline]
>   __sock_sendmsg net/socket.c:745 [inline]
>   sock_write_iter+0x4b8/0x5c0 net/socket.c:1160
>   new_sync_write fs/read_write.c:497 [inline]
>   vfs_write+0x6b6/0x1140 fs/read_write.c:590
>   ksys_write+0x1f8/0x260 fs/read_write.c:643
>   do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>   do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> Fixes: 52e1635631b3 ("[IPV6]: ROUTE: Add router_probe_interval sysctl.")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Reviewed-by: Jason Xing <kerneljasonxing@...il.com>