netdev - Re: [PATCH net] kcm: avoid potential race in kcm_tx

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: <CACT4Y+YQ39dVh0tbmjzqoNEnS76ucbVYiNrfwjiby-8z6E7UDQ@mail.gmail.com>
Date:   Wed, 12 Oct 2022 16:00:34 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        eric.dumazet@...il.com, syzbot <syzkaller@...glegroups.com>,
        Tom Herbert <tom@...bertland.com>
Subject: Re: [PATCH net] kcm: avoid potential race in kcm_tx_work

On Wed, 12 Oct 2022 at 15:34, 'Eric Dumazet' via syzkaller
<syzkaller@...glegroups.com> wrote:
>
> syzbot found that kcm_tx_work() could crash [1] in:
>
>         /* Primarily for SOCK_SEQPACKET sockets */
>         if (likely(sk->sk_socket) &&
>             test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
> <<*>>   clear_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
>                 sk->sk_write_space(sk);
>         }
>
> I think the reason is that another thread might concurrently
> run in kcm_release() and call sock_orphan(sk) while sk is not
> locked. kcm_tx_work() find sk->sk_socket being NULL.

Does it make sense to add some lockdep annotations to sock_orphan()
and maybe some other similar functions to catch such cases earlier?


> [1]
> BUG: KASAN: null-ptr-deref in instrument_atomic_write include/linux/instrumented.h:86 [inline]
> BUG: KASAN: null-ptr-deref in clear_bit include/asm-generic/bitops/instrumented-atomic.h:41 [inline]
> BUG: KASAN: null-ptr-deref in kcm_tx_work+0xff/0x160 net/kcm/kcmsock.c:742
> Write of size 8 at addr 0000000000000008 by task kworker/u4:3/53
>
> CPU: 0 PID: 53 Comm: kworker/u4:3 Not tainted 5.19.0-rc3-next-20220621-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Workqueue: kkcmd kcm_tx_work
> Call Trace:
> <TASK>
> __dump_stack lib/dump_stack.c:88 [inline]
> dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
> kasan_report+0xbe/0x1f0 mm/kasan/report.c:495
> check_region_inline mm/kasan/generic.c:183 [inline]
> kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189
> instrument_atomic_write include/linux/instrumented.h:86 [inline]
> clear_bit include/asm-generic/bitops/instrumented-atomic.h:41 [inline]
> kcm_tx_work+0xff/0x160 net/kcm/kcmsock.c:742
> process_one_work+0x996/0x1610 kernel/workqueue.c:2289
> worker_thread+0x665/0x1080 kernel/workqueue.c:2436
> kthread+0x2e9/0x3a0 kernel/kthread.c:376
> ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:302
> </TASK>
>
> Fixes: ab7ac4eb9832 ("kcm: Kernel Connection Multiplexor module")
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Tom Herbert <tom@...bertland.com>
> ---
>  net/kcm/kcmsock.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
> index 1215c863e1c410fa9ba5b9c3706152decfb3ebac..27725464ec08fe2b5f2e86202636cbc895568098 100644
> --- a/net/kcm/kcmsock.c
> +++ b/net/kcm/kcmsock.c
> @@ -1838,10 +1838,10 @@ static int kcm_release(struct socket *sock)
>         kcm = kcm_sk(sk);
>         mux = kcm->mux;
>
> +       lock_sock(sk);
>         sock_orphan(sk);
>         kfree_skb(kcm->seq_skb);
>
> -       lock_sock(sk);
>         /* Purge queue under lock to avoid race condition with tx_work trying
>          * to act when queue is nonempty. If tx_work runs after this point
>          * it will just return.
> --
> 2.38.0.rc1.362.ged0d419d3c-goog
>
> --
> You received this message because you are subscribed to the Google Groups "syzkaller" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller+unsubscribe@...glegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller/20221012133412.519394-1-edumazet%40google.com.