netdev - Re: [PATCH net] udp: annotate data-races around up->pending

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Date: Fri, 12 Jan 2024 13:56:19 +0100
From: Jiri Pirko <jiri@...nulli.us>
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>,
	Willem de Bruijn <willemb@...gle.com>, netdev@...r.kernel.org,
	eric.dumazet@...il.com,
	syzbot+8d482d0e407f665d9d10@...kaller.appspotmail.com
Subject: Re: [PATCH net] udp: annotate data-races around up->pending

Fri, Jan 12, 2024 at 11:44:27AM CET, edumazet@...gle.com wrote:
>up->pending can be read without holding the socket lock,
>as pointed out by syzbot [1]
>
>Add READ_ONCE() in lockless contexts, and WRITE_ONCE()
>on write side.
>
>[1]
>BUG: KCSAN: data-race in udpv6_sendmsg / udpv6_sendmsg
>
>write to 0xffff88814e5eadf0 of 4 bytes by task 15547 on cpu 1:
> udpv6_sendmsg+0x1405/0x1530 net/ipv6/udp.c:1596
> inet6_sendmsg+0x63/0x80 net/ipv6/af_inet6.c:657
> sock_sendmsg_nosec net/socket.c:730 [inline]
> __sock_sendmsg net/socket.c:745 [inline]
> __sys_sendto+0x257/0x310 net/socket.c:2192
> __do_sys_sendto net/socket.c:2204 [inline]
> __se_sys_sendto net/socket.c:2200 [inline]
> __x64_sys_sendto+0x78/0x90 net/socket.c:2200
> do_syscall_x64 arch/x86/entry/common.c:52 [inline]
> do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
> entry_SYSCALL_64_after_hwframe+0x63/0x6b
>
>read to 0xffff88814e5eadf0 of 4 bytes by task 15551 on cpu 0:
> udpv6_sendmsg+0x22c/0x1530 net/ipv6/udp.c:1373
> inet6_sendmsg+0x63/0x80 net/ipv6/af_inet6.c:657
> sock_sendmsg_nosec net/socket.c:730 [inline]
> __sock_sendmsg net/socket.c:745 [inline]
> ____sys_sendmsg+0x37c/0x4d0 net/socket.c:2586
> ___sys_sendmsg net/socket.c:2640 [inline]
> __sys_sendmmsg+0x269/0x500 net/socket.c:2726
> __do_sys_sendmmsg net/socket.c:2755 [inline]
> __se_sys_sendmmsg net/socket.c:2752 [inline]
> __x64_sys_sendmmsg+0x57/0x60 net/socket.c:2752
> do_syscall_x64 arch/x86/entry/common.c:52 [inline]
> do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
> entry_SYSCALL_64_after_hwframe+0x63/0x6b
>
>value changed: 0x00000000 -> 0x0000000a
>
>Reported by Kernel Concurrency Sanitizer on:
>CPU: 0 PID: 15551 Comm: syz-executor.1 Tainted: G        W          6.7.0-syzkaller #0
>Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
>
>Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
>Reported-by: syzbot+8d482d0e407f665d9d10@...kaller.appspotmail.com
>Link: https://lore.kernel.org/netdev/0000000000009e46c3060ebcdffd@google.com/
>Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Reviewed-by: Jiri Pirko <jiri@...dia.com>