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From:   Cong Wang <xiyou.wangcong@gmail.com>
Date:   Tue, 6 Apr 2021 10:58:23 -0700
Message-ID: <CAM_iQpU9gSy++6Ba0vfnHz_J4-FcGpAMG7yzFDFk+qTi1DJnwA@mail.gmail.com>
Subject: Re: [syzbot] WARNING: suspicious RCU usage in tcp_bpf_update_proto
To:     syzbot <syzbot+320a3bc8d80f478c37e4@syzkaller.appspotmail.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Andrii Nakryiko <andrii@kernel.org>, anton@tuxera.com,
        Alexei Starovoitov <ast@kernel.org>,
        Borislav Petkov <bp@alien8.de>, bpf <bpf@vger.kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        David Miller <davem@davemloft.net>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Jakub Sitnicki <jakub@cloudflare.com>, jmattson@google.com,
        John Fastabend <john.fastabend@gmail.com>,
        Joerg Roedel <joro@8bytes.org>,
        Martin KaFai Lau <kafai@fb.com>, kpsingh@kernel.org,
        Jakub Kicinski <kuba@kernel.org>,
        "kvm@vger.kernel.org list" <kvm@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Lorenz Bauer <lmb@cloudflare.com>,
        Ingo Molnar <mingo@redhat.com>,
        Linux Kernel Network Developers <netdev@vger.kernel.org>,
        pbonzini@redhat.com, rkovhaev@gmail.com, seanjc@google.com,
        Song Liu <songliubraving@fb.com>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        vkuznets@redhat.com, wanpengli@tencent.com, x86 <x86@kernel.org>,
        Yonghong Song <yhs@fb.com>
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On Tue, Apr 6, 2021 at 2:44 AM syzbot
<syzbot+320a3bc8d80f478c37e4@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    514e1150 net: x25: Queue received packets in the drivers i..
> git tree:       net-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=112a8831d00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=7eff0f22b8563a5f
> dashboard link: https://syzkaller.appspot.com/bug?extid=320a3bc8d80f478c37e4
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1532d711d00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15f44c5ed00000
>
> The issue was bisected to:
>
> commit 4dfe6bd94959222e18d512bdf15f6bf9edb9c27c
> Author: Rustam Kovhaev <rkovhaev@gmail.com>
> Date:   Wed Feb 24 20:00:30 2021 +0000
>
>     ntfs: check for valid standard information attribute

This is caused by one of my sockmap patches.

>
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=16207a81d00000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=15207a81d00000
> console output: https://syzkaller.appspot.com/x/log.txt?x=11207a81d00000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+320a3bc8d80f478c37e4@syzkaller.appspotmail.com
> Fixes: 4dfe6bd94959 ("ntfs: check for valid standard information attribute")
>
> =============================
> WARNING: suspicious RCU usage
> 5.12.0-rc4-syzkaller #0 Not tainted
> -----------------------------
> include/linux/skmsg.h:286 suspicious rcu_dereference_check() usage!
>
> other info that might help us debug this:
>
>
> rcu_scheduler_active = 2, debug_locks = 1
> 1 lock held by syz-executor383/8454:
>  #0: ffff888013a99b48 (clock-AF_INET){++..}-{2:2}, at: sk_psock_drop+0x2c/0x460 net/core/skmsg.c:788
>
> stack backtrace:
> CPU: 1 PID: 8454 Comm: syz-executor383 Not tainted 5.12.0-rc4-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:79 [inline]
>  dump_stack+0x141/0x1d7 lib/dump_stack.c:120
>  sk_psock include/linux/skmsg.h:286 [inline]
>  tcp_bpf_update_proto+0x530/0x5f0 net/ipv4/tcp_bpf.c:504
>  sk_psock_restore_proto include/linux/skmsg.h:408 [inline]
>  sk_psock_drop+0xdf/0x460 net/core/skmsg.c:789
>  sk_psock_put include/linux/skmsg.h:446 [inline]
>  tcp_bpf_recvmsg+0x42d/0x480 net/ipv4/tcp_bpf.c:208
>  inet_recvmsg+0x11b/0x5d0 net/ipv4/af_inet.c:852

Oddly, I have all relevant Kconfig enabled but never see this
warning when running selftests for hours....

Anyway, let me see how this should be fixed.

Thanks!