netdev - Re: [PATCH v1 net] af_packet: Fix data-races of pkt

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Date: Thu, 25 May 2023 11:23:43 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Kuniyuki Iwashima <kuniyu@...zon.com>
Cc: "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Pavel Emelyanov <xemul@...allels.com>, Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org, 
	syzkaller <syzkaller@...glegroups.com>
Subject: Re: [PATCH v1 net] af_packet: Fix data-races of pkt_sk(sk)->num.

On Wed, May 24, 2023 at 7:30 PM Kuniyuki Iwashima <kuniyu@...zon.com> wrote:
>
> syzkaller found a data race of pkt_sk(sk)->num.
>
> The value is changed under lock_sock() and po->bind_lock, so we
> need READ_ONCE() to access pkt_sk(sk)->num without these locks in
> packet_bind_spkt(), packet_bind(), and sk_diag_fill().
>
> Note that WRITE_ONCE() is already added by commit c7d2ef5dd4b0
> ("net/packet: annotate accesses to po->bind").
>
> BUG: KCSAN: data-race in packet_bind / packet_do_bind
>
> write (marked) to 0xffff88802ffd1cee of 2 bytes by task 7322 on cpu 0:
>  packet_do_bind+0x446/0x640 net/packet/af_packet.c:3236
>  packet_bind+0x99/0xe0 net/packet/af_packet.c:3321
>  __sys_bind+0x19b/0x1e0 net/socket.c:1803
>  __do_sys_bind net/socket.c:1814 [inline]
>  __se_sys_bind net/socket.c:1812 [inline]
>  __x64_sys_bind+0x40/0x50 net/socket.c:1812
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x3b/0x90 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x72/0xdc
>
> read to 0xffff88802ffd1cee of 2 bytes by task 7318 on cpu 1:
>  packet_bind+0xbf/0xe0 net/packet/af_packet.c:3322
>  __sys_bind+0x19b/0x1e0 net/socket.c:1803
>  __do_sys_bind net/socket.c:1814 [inline]
>  __se_sys_bind net/socket.c:1812 [inline]
>  __x64_sys_bind+0x40/0x50 net/socket.c:1812
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x3b/0x90 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x72/0xdc
>
> value changed: 0x0300 -> 0x0000
>
> Reported by Kernel Concurrency Sanitizer on:
> CPU: 1 PID: 7318 Comm: syz-executor.4 Not tainted 6.3.0-13380-g7fddb5b5300c #4
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
>
> Fixes: 96ec6327144e ("packet: Diag core and basic socket info dumping")
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Reported-by: syzkaller <syzkaller@...glegroups.com>
> Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>

Reviewed-by: Willem de Bruijn <willemb@...gle.com>