netdev - Re: [PATCH net 3/3] nfc: llcp: fix nfc_llcp

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Date: Tue, 9 Apr 2024 08:17:52 +0200
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Eric Dumazet <edumazet@...gle.com>, "David S . Miller"
 <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>
Cc: Simon Horman <horms@...nel.org>, netdev@...r.kernel.org,
 eric.dumazet@...il.com, syzbot <syzkaller@...glegroups.com>
Subject: Re: [PATCH net 3/3] nfc: llcp: fix nfc_llcp_setsockopt() unsafe
 copies

On 08/04/2024 10:28, Eric Dumazet wrote:
> syzbot reported unsafe calls to copy_from_sockptr() [1]
> 
> Use copy_safe_from_sockptr() instead.
> 
> [1]
> 
> BUG: KASAN: slab-out-of-bounds in copy_from_sockptr_offset include/linux/sockptr.h:49 [inline]
>  BUG: KASAN: slab-out-of-bounds in copy_from_sockptr include/linux/sockptr.h:55 [inline]
>  BUG: KASAN: slab-out-of-bounds in nfc_llcp_setsockopt+0x6c2/0x850 net/nfc/llcp_sock.c:255
> Read of size 4 at addr ffff88801caa1ec3 by task syz-executor459/5078
> 
> CPU: 0 PID: 5078 Comm: syz-executor459 Not tainted 6.8.0-syzkaller-08951-gfe46a7dd189e #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
> Call Trace:
>  <TASK>
>   __dump_stack lib/dump_stack.c:88 [inline]
>   dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
>   print_address_description mm/kasan/report.c:377 [inline]
>   print_report+0x169/0x550 mm/kasan/report.c:488
>   kasan_report+0x143/0x180 mm/kasan/report.c:601
>   copy_from_sockptr_offset include/linux/sockptr.h:49 [inline]
>   copy_from_sockptr include/linux/sockptr.h:55 [inline]
>   nfc_llcp_setsockopt+0x6c2/0x850 net/nfc/llcp_sock.c:255
>   do_sock_setsockopt+0x3b1/0x720 net/socket.c:2311
>   __sys_setsockopt+0x1ae/0x250 net/socket.c:2334
>   __do_sys_setsockopt net/socket.c:2343 [inline]
>   __se_sys_setsockopt net/socket.c:2340 [inline]
>   __x64_sys_setsockopt+0xb5/0xd0 net/socket.c:2340
>  do_syscall_64+0xfd/0x240
>  entry_SYSCALL_64_after_hwframe+0x6d/0x75
> RIP: 0033:0x7f7fac07fd89
> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 91 18 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007fff660eb788 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f7fac07fd89
> RDX: 0000000000000000 RSI: 0000000000000118 RDI: 0000000000000004
> RBP: 0000000000000000 R08: 0000000000000002 R09: 0000000000000000
> R10: 0000000020000a80 R11: 0000000000000246 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Cc: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>

I received only this patch, so I don't know what
copy_safe_from_sockptr() is doing, but I guess it respects amount of
data in optval, so looks reasonable.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>

Best regards,
Krzysztof