netdev - Re: [PATCH net] ipv6: fix potential NULL deref in fib6

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Message-ID: <4930145b-7f45-4fb0-90cb-ff1d5e265abe@kernel.org>
Date: Wed, 29 Nov 2023 16:04:27 -0700
From: David Ahern <dsahern@...nel.org>
To: Eric Dumazet <edumazet@...gle.com>, "David S . Miller"
 <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, eric.dumazet@...il.com,
 syzbot <syzkaller@...glegroups.com>, Wei Wang <weiwan@...gle.com>
Subject: Re: [PATCH net] ipv6: fix potential NULL deref in fib6_add()

On 11/29/23 9:06 AM, Eric Dumazet wrote:
> If fib6_find_prefix() returns NULL, we should silently fallback
> using fib6_null_entry regardless of RT6_DEBUG value.
> 
> syzbot reported:
> 
> WARNING: CPU: 0 PID: 5477 at net/ipv6/ip6_fib.c:1516 fib6_add+0x310d/0x3fa0 net/ipv6/ip6_fib.c:1516
> Modules linked in:
> CPU: 0 PID: 5477 Comm: syz-executor.0 Not tainted 6.7.0-rc2-syzkaller-00029-g9b6de136b5f0 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/10/2023
> RIP: 0010:fib6_add+0x310d/0x3fa0 net/ipv6/ip6_fib.c:1516
> Code: 00 48 8b 54 24 68 e8 42 22 00 00 48 85 c0 74 14 49 89 c6 e8 d5 d3 c2 f7 eb 5d e8 ce d3 c2 f7 e9 ca 00 00 00 e8 c4 d3 c2 f7 90 <0f> 0b 90 48 b8 00 00 00 00 00 fc ff df 48 8b 4c 24 38 80 3c 01 00
> RSP: 0018:ffffc90005067740 EFLAGS: 00010293
> RAX: ffffffff89cba5bc RBX: ffffc90005067ab0 RCX: ffff88801a2e9dc0
> RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
> RBP: ffffc90005067980 R08: ffffffff89cbca85 R09: 1ffff110040d4b85
> R10: dffffc0000000000 R11: ffffed10040d4b86 R12: 00000000ffffffff
> R13: 1ffff110051c3904 R14: ffff8880206a5c00 R15: ffff888028e1c820
> FS: 00007f763783c6c0(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f763783bff8 CR3: 000000007f74d000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
> <TASK>
> __ip6_ins_rt net/ipv6/route.c:1303 [inline]
> ip6_route_add+0x88/0x120 net/ipv6/route.c:3847
> ipv6_route_ioctl+0x525/0x7b0 net/ipv6/route.c:4467
> inet6_ioctl+0x21a/0x270 net/ipv6/af_inet6.c:575
> sock_do_ioctl+0x152/0x460 net/socket.c:1220
> sock_ioctl+0x615/0x8c0 net/socket.c:1339
> vfs_ioctl fs/ioctl.c:51 [inline]
> __do_sys_ioctl fs/ioctl.c:871 [inline]
> __se_sys_ioctl+0xf8/0x170 fs/ioctl.c:857
> do_syscall_x64 arch/x86/entry/common.c:51 [inline]
> do_syscall_64+0x45/0x110 arch/x86/entry/common.c:82
> 
> Fixes: 7bbfe00e0252 ("ipv6: fix general protection fault in fib6_add()")
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Wei Wang <weiwan@...gle.com>
> ---
>  net/ipv6/ip6_fib.c | 6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)
> 

Reviewed-by: David Ahern <dsahern@...nel.org>