netdev - Re: [PATCH net-next] net: annotate data-races around sock->ops

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Date: Tue, 8 Aug 2023 11:14:25 -0700
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: <edumazet@...gle.com>
CC: <davem@...emloft.net>, <eric.dumazet@...il.com>, <kuba@...nel.org>,
	<netdev@...r.kernel.org>, <pabeni@...hat.com>, <syzkaller@...glegroups.com>,
	Kuniyuki Iwashima <kuniyu@...zon.com>
Subject: Re: [PATCH net-next] net: annotate data-races around sock->ops

From: Eric Dumazet <edumazet@...gle.com>
Date: Tue,  8 Aug 2023 13:58:09 +0000
> IPV6_ADDRFORM socket option is evil, because it can change sock->ops
> while other threads might read it. Same issue for sk->sk_family
> being set to AF_INET.
> 
> Adding READ_ONCE() over sock->ops reads is needed for sockets
> that might be impacted by IPV6_ADDRFORM.
> 
> Note that mptcp_is_tcpsk() can also overwrite sock->ops.
> 
> Adding annotations for all sk->sk_family reads will require
> more patches :/
> 
> BUG: KCSAN: data-race in ____sys_sendmsg / do_ipv6_setsockopt
> 
> write to 0xffff888109f24ca0 of 8 bytes by task 4470 on cpu 0:
> do_ipv6_setsockopt+0x2c5e/0x2ce0 net/ipv6/ipv6_sockglue.c:491
> ipv6_setsockopt+0x57/0x130 net/ipv6/ipv6_sockglue.c:1012
> udpv6_setsockopt+0x95/0xa0 net/ipv6/udp.c:1690
> sock_common_setsockopt+0x61/0x70 net/core/sock.c:3663
> __sys_setsockopt+0x1c3/0x230 net/socket.c:2273
> __do_sys_setsockopt net/socket.c:2284 [inline]
> __se_sys_setsockopt net/socket.c:2281 [inline]
> __x64_sys_setsockopt+0x66/0x80 net/socket.c:2281
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> read to 0xffff888109f24ca0 of 8 bytes by task 4469 on cpu 1:
> sock_sendmsg_nosec net/socket.c:724 [inline]
> sock_sendmsg net/socket.c:747 [inline]
> ____sys_sendmsg+0x349/0x4c0 net/socket.c:2503
> ___sys_sendmsg net/socket.c:2557 [inline]
> __sys_sendmmsg+0x263/0x500 net/socket.c:2643
> __do_sys_sendmmsg net/socket.c:2672 [inline]
> __se_sys_sendmmsg net/socket.c:2669 [inline]
> __x64_sys_sendmmsg+0x57/0x60 net/socket.c:2669
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> value changed: 0xffffffff850e32b8 -> 0xffffffff850da890
> 
> Reported by Kernel Concurrency Sanitizer on:
> CPU: 1 PID: 4469 Comm: syz-executor.1 Not tainted 6.4.0-rc5-syzkaller-00313-g4c605260bc60 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/25/2023
> 
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Reviewed-by: Kuniyuki Iwashima <kuniyu@...zon.com>