netdev - Re: [PATCH net] net: annotate sk->sk_err write from do

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Date: Tue, 9 May 2023 15:53:37 -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>,
	<kuniyu@...zon.com>
Subject: Re: [PATCH net] net: annotate sk->sk_err write from do_recvmmsg()

From: Eric Dumazet <edumazet@...gle.com>
Date: Tue,  9 May 2023 16:35:53 +0000
> do_recvmmsg() can write to sk->sk_err from multiple threads.
> 
> As said before, many other points reading or writing sk_err
> need annotations.
> 
> Fixes: 34b88a68f26a ("net: Fix use after free in the recvmmsg exit path")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: syzbot <syzkaller@...glegroups.com>

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


> ---
>  net/socket.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/socket.c b/net/socket.c
> index a7b4b37d86df7a9232d582a14863c05b5fd34b68..b7e01d0fe0824d1f277c1fe70f68f09a10319832 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -2911,7 +2911,7 @@ static int do_recvmmsg(int fd, struct mmsghdr __user *mmsg,
>  		 * error to return on the next call or if the
>  		 * app asks about it using getsockopt(SO_ERROR).
>  		 */
> -		sock->sk->sk_err = -err;
> +		WRITE_ONCE(sock->sk->sk_err, -err);
>  	}
>  out_put:
>  	fput_light(sock->file, fput_needed);
> -- 
> 2.40.1.521.gf1e218fcd8-goog