netdev - Re: [PATCH v2 net-next] tcp: Warn if sock_owned_by_user() is true in tcp_child

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20211209110746.91987-1-kuniyu@amazon.co.jp>
Date:   Thu, 9 Dec 2021 20:07:46 +0900
From:   Kuniyuki Iwashima <kuniyu@...zon.co.jp>
To:     <edumazet@...gle.com>
CC:     <benh@...zon.com>, <davem@...emloft.net>, <kuba@...nel.org>,
        <kuni1840@...il.com>, <kuniyu@...zon.co.jp>,
        <netdev@...r.kernel.org>
Subject: Re: [PATCH v2 net-next] tcp: Warn if sock_owned_by_user() is true in tcp_child_process().

From:   Eric Dumazet <edumazet@...gle.com>
Date:   Thu, 9 Dec 2021 00:00:35 -0800
> On Wed, Dec 8, 2021 at 5:33 PM Kuniyuki Iwashima <kuniyu@...zon.co.jp> wrote:
>>
>> While creating a child socket from ACK (not TCP Fast Open case), before
>> v2.3.41, we used to call bh_lock_sock() later than now; it was called just
>> before tcp_rcv_state_process().  The full socket was put into an accept
>> queue and exposed to other CPUs before bh_lock_sock() so that process
>> context might have acquired the lock by then.  Thus, we had to check if any
>> process context was accessing the socket before tcp_rcv_state_process().
>>
> 
> I think you misunderstood me.
> 
> I think this code is not dead yet, so I would :
> 
> Not include a Fixes: tag to avoid unnecessary backports (of a patch
> and its revert)
> 
> If you want to get syzbot coverage for few releases, especially with
> MPTCP and synflood,
> you  can then submit a patch like the following.

Sorry, I got on the same page.
Let me take a look at MPTCP, then if I still think it is dead code, I will
submit the patch.

Thank you.


> 
> diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
> index cf913a66df17..19da6e442fca 100644
> --- a/net/ipv4/tcp_minisocks.c
> +++ b/net/ipv4/tcp_minisocks.c
> @@ -843,6 +843,9 @@ int tcp_child_process(struct sock *parent, struct
> sock *child,
>                  * in main socket hash table and lock on listening
>                  * socket does not protect us more.
>                  */
> +
> +               /* Check if this code path is obsolete ? */
> +               WARN_ON_ONCE(1);
>                 __sk_add_backlog(child, skb);
>         }