Date:   Sun, 1 Apr 2018 12:34:58 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+c7b0dde061c523bc4b0f@...kaller.appspotmail.com>
Cc:     David Miller <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        LKML <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>, syzkaller-bugs@...glegroups.com,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>
Subject: Re: WARNING in refcount_sub_and_test (2)

On Fri, Mar 30, 2018 at 12:01 AM, syzbot
<syzbot+c7b0dde061c523bc4b0f@...kaller.appspotmail.com> wrote:
> Hello,
>
> syzbot hit the following crash on bpf-next commit
> 22527437e0a0c96ee3153e9d0382942b0fd4f9dd (Thu Mar 29 02:36:15 2018 +0000)
> Merge branch 'nfp-bpf-updates'
> syzbot dashboard link:
> https://syzkaller.appspot.com/bug?extid=c7b0dde061c523bc4b0f
>
> C reproducer: https://syzkaller.appspot.com/x/repro.c?id=5996614741131264
> syzkaller reproducer:
> https://syzkaller.appspot.com/x/repro.syz?id=5947747274326016
> Raw console output:
> https://syzkaller.appspot.com/x/log.txt?id=6215237837520896
> Kernel config:
> https://syzkaller.appspot.com/x/.config?id=-1280663959502969741
> compiler: gcc (GCC) 7.1.1 20170620
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+c7b0dde061c523bc4b0f@...kaller.appspotmail.com
> It will help syzbot understand when the bug is fixed. See footer for
> details.
> If you forward the report, please keep this part and the footer.

Messed kernel output.

#syz dup: WARNING: refcount bug in sk_alloc



> R13: 0030656c69662f2e R14: 0000000000000005 R15: 2f30656c69662f2e
> ------------[ cut here ]------------
> ------------[ cut here ]------------
> refcount_t: increment on 0; use-after-free.
> refcount_t: underflow; use-after-free.
> WARNING: CPU: 0 PID: 4450 at lib/refcount.c:187
> refcount_sub_and_test+0x167/0x1b0 lib/refcount.c:187
> WARNING: CPU: 1 PID: 4460 at lib/refcount.c:153 refcount_inc+0x47/0x50
> lib/refcount.c:153
> Kernel panic - not syncing: panic_on_warn set ...
>
> Modules linked in:
> CPU: 0 PID: 4450 Comm: syzkaller428798 Not tainted 4.16.0-rc6+ #40
> CPU: 1 PID: 4460 Comm: syzkaller428798 Not tainted 4.16.0-rc6+ #40
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
> RIP: 0010:refcount_inc+0x47/0x50 lib/refcount.c:153
>  __dump_stack lib/dump_stack.c:17 [inline]
>  dump_stack+0x194/0x24d lib/dump_stack.c:53
> RSP: 0018:ffff8801b534f860 EFLAGS: 00010286
> RAX: dffffc0000000008 RBX: ffff8801b1b8c184 RCX: ffffffff815ba4be
>  panic+0x1e4/0x41c kernel/panic.c:183
> RDX: 0000000000000000 RSI: 1ffff10036a69ebc RDI: 1ffff10036a69e91
> RBP: ffff8801b534f868 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801b534faf8
> R13: ffff8801b04db513 R14: ffff8801b1b8c180 R15: ffff8801b04db501
> FS:  00000000008e6880(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>  __warn+0x1dc/0x200 kernel/panic.c:547
> CR2: 00000000006ea510 CR3: 00000001b106f005 CR4: 00000000001606e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>  report_bug+0x1f4/0x2b0 lib/bug.c:186
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>  fixup_bug.part.11+0x37/0x80 arch/x86/kernel/traps.c:178
> Call Trace:
>  fixup_bug arch/x86/kernel/traps.c:247 [inline]
>  do_error_trap+0x2d7/0x3e0 arch/x86/kernel/traps.c:296
>  get_net include/net/net_namespace.h:204 [inline]
>  sk_alloc+0x3f9/0x1440 net/core/sock.c:1540
>  do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315
>  invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:986
> RIP: 0010:refcount_sub_and_test+0x167/0x1b0 lib/refcount.c:187
> RSP: 0018:ffff8801b0e87728 EFLAGS: 00010286
> RAX: dffffc0000000008 RBX: 0000000000000000 RCX: ffffffff815ba4be
> RDX: 0000000000000000 RSI: 1ffff100361d0e95 RDI: 0000000000000293
> RBP: ffff8801b0e877b8 R08: 0000000000000000 R09: 0000000000000000
> R10: ffff8801b0e87850 R11: 0000000000000000 R12: 1ffff100361d0ee6
>  inet_create+0x47c/0xf50 net/ipv4/af_inet.c:320
> R13: 00000000ffffffff R14: 0000000000000001 R15: ffff8801b0816204
>  __sock_create+0x4d4/0x850 net/socket.c:1285
>  sock_create net/socket.c:1325 [inline]
>  SYSC_socket net/socket.c:1355 [inline]
>  SyS_socket+0xeb/0x1d0 net/socket.c:1335
>  refcount_dec_and_test+0x1a/0x20 lib/refcount.c:212
>  put_net include/net/net_namespace.h:222 [inline]
>  __sk_destruct+0x560/0x920 net/core/sock.c:1592
>  do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
>  sk_destruct+0x47/0x80 net/core/sock.c:1601
>  entry_SYSCALL_64_after_hwframe+0x42/0xb7
>  __sk_free+0xf1/0x2b0 net/core/sock.c:1612
> RIP: 0033:0x44ac67
>  sk_free+0x2a/0x40 net/core/sock.c:1623
> RSP: 002b:00007ffcd4f45588 EFLAGS: 00000202
>  sock_put include/net/sock.h:1660 [inline]
>  tcp_close+0x967/0x1190 net/ipv4/tcp.c:2321
>  ORIG_RAX: 0000000000000029
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000044ac67
> RDX: 0000000000000006 RSI: 0000000000000001 RDI: 0000000000000002
> RBP: 00007ffcd4f456b0 R08: 0000000000000000 R09: 0000000000000001
> R10: 0000000000000006 R11: 0000000000000202 R12: 0000000000000002
>  inet_release+0xed/0x1c0 net/ipv4/af_inet.c:427
> R13: 0000000000000002 R14: 000000000000b38f R15: 00007ffcd4f456d8
>  sock_release+0x8d/0x1e0 net/socket.c:594
> Code:
> be
>  sock_close+0x16/0x20 net/socket.c:1149
> fe
>  __fput+0x327/0x7e0 fs/file_table.c:209
> 5b
> 5d
> c3
>  ____fput+0x15/0x20 fs/file_table.c:243
> e8
>  task_work_run+0x199/0x270 kernel/task_work.c:113
> 5a
> 3c
> be
> fe
>  tracehook_notify_resume include/linux/tracehook.h:191 [inline]
>  exit_to_usermode_loop+0x275/0x2f0 arch/x86/entry/common.c:166
> 80
> 3d
> 91
>  prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
>  syscall_return_slowpath arch/x86/entry/common.c:265 [inline]
>  do_syscall_64+0x6ec/0x940 arch/x86/entry/common.c:292
> f5
> 84
> 05
> 00 75 ea e8 4c 3c be
> fe
> 48
> c7
> c7
>  entry_SYSCALL_64_after_hwframe+0x42/0xb7
> 80
> RIP: 0033:0x406fe0
> 78
> RSP: 002b:00007ffcd4f45588 EFLAGS: 00000246
> e5
>  ORIG_RAX: 0000000000000003
> 86
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000406fe0
> c6
> RDX: 00000000000000e0 RSI: 00007ffcd4f45e70 RDI: 0000000000000003
> 05
> RBP: 00007ffcd4f456b0 R08: 00007ffcd4f455b0 R09: 0000000000000001
> 7c
> R10: 00007ffcd4f456b0 R11: 0000000000000246 R12: 00000000006de4c0
> R13: 00000000006dde40 R14: 0000000000001380 R15: 00007ffcd4f456d8
> f5 84 05 01 e8 f9 47 8e fe <0f> 0b eb ce 0f 1f 44 00 00 55 48 89 e5 41 57 41
> 56 41 55 41 54
> ---[ end trace 04af8119701e2164 ]---
> Dumping ftrace buffer:
>    (ftrace buffer empty)
> Kernel Offset: disabled
> Rebooting in 86400 seconds..
>
>
> ---
> This bug is generated by a dumb bot. It may contain errors.
> See https://goo.gl/tpsmEJ for details.
> Direct all questions to syzkaller@...glegroups.com.
>
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> merged
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