WARNING: refcount bug in sock_wfree

[syzbot]

Hello,

syzbot hit the following crash on upstream commit
79c0ef3e85c015b0921a8fd5dd539d1480e9cd6c (Mon Feb 19 19:58:19 2018 +0000)
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net

So far this crash happened 2 times on
https://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git/master.
syzkaller reproducer is attached.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+98a809...@syzkaller.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.

IPv6: ADDRCONF(NETDEV_UP): bridge0: link is not ready
IPv6: ADDRCONF(NETDEV_UP): bridge0: link is not ready
audit: type=1400 audit(1519151768.973:11): avc: denied { sys_chroot }
for pid=4169 comm="syz-executor5" capability=18
scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023
tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=cap_userns
permissive=1
------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 0 PID: 5074 at lib/refcount.c:187
refcount_sub_and_test+0x167/0x1b0 lib/refcount.c:187
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 5074 Comm: syz-executor5 Not tainted 4.16.0-rc2+ #322
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x194/0x257 lib/dump_stack.c:53
panic+0x1e4/0x41c kernel/panic.c:183
__warn+0x1dc/0x200 kernel/panic.c:547
report_bug+0x211/0x2d0 lib/bug.c:184
fixup_bug.part.11+0x37/0x80 arch/x86/kernel/traps.c:178
fixup_bug arch/x86/kernel/traps.c:247 [inline]
do_error_trap+0x2d7/0x3e0 arch/x86/kernel/traps.c:296
do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315
invalid_op+0x58/0x80 arch/x86/entry/entry_64.S:957
RIP: 0010:refcount_sub_and_test+0x167/0x1b0 lib/refcount.c:187
RSP: 0018:ffff8801cf2b6490 EFLAGS: 00010282
RAX: dffffc0000000008 RBX: 0000000000000401 RCX: ffffffff815abdbe
RDX: 0000000000000000 RSI: 1ffff10039e56c42 RDI: 1ffff10039e56c17
RBP: ffff8801cf2b6520 R08: 1ffff10039e56bd9 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 1ffff10039e56c93
R13: 00000000ffffff01 R14: 0000000000000500 R15: ffff8801ae3c69fc
sock_wfree+0xa6/0x140 net/core/sock.c:1819
sctp_wfree+0x2eb/0x670 net/sctp/socket.c:8065
skb_release_head_state+0x124/0x260 net/core/skbuff.c:612
skb_release_all+0x15/0x60 net/core/skbuff.c:625
__kfree_skb net/core/skbuff.c:641 [inline]
consume_skb+0x153/0x490 net/core/skbuff.c:701
sctp_chunk_destroy net/sctp/sm_make_chunk.c:1450 [inline]
sctp_chunk_put+0x29c/0x420 net/sctp/sm_make_chunk.c:1477
sctp_chunk_free+0x53/0x60 net/sctp/sm_make_chunk.c:1464
__sctp_outq_teardown+0x244/0x1230 net/sctp/outqueue.c:234
sctp_outq_free+0x15/0x20 net/sctp/outqueue.c:291
sctp_association_free+0x2d0/0x930 net/sctp/associola.c:356
sctp_cmd_delete_tcb net/sctp/sm_sideeffect.c:939 [inline]
sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1343 [inline]
sctp_side_effects net/sctp/sm_sideeffect.c:1210 [inline]
sctp_do_sm+0x32e3/0x6ed0 net/sctp/sm_sideeffect.c:1181
sctp_primitive_ABORT+0xa0/0xd0 net/sctp/primitive.c:119
sctp_close+0x266/0x9a0 net/sctp/socket.c:1539
inet_release+0xed/0x1c0 net/ipv4/af_inet.c:427
sock_release+0x8d/0x1e0 net/socket.c:595
sock_close+0x16/0x20 net/socket.c:1149
__fput+0x327/0x7e0 fs/file_table.c:209
____fput+0x15/0x20 fs/file_table.c:243
task_work_run+0x199/0x270 kernel/task_work.c:113
exit_task_work include/linux/task_work.h:22 [inline]
do_exit+0x9bb/0x1ad0 kernel/exit.c:865
do_group_exit+0x149/0x400 kernel/exit.c:968
get_signal+0x73a/0x16d0 kernel/signal.c:2469
do_signal+0x90/0x1e90 arch/x86/kernel/signal.c:809
exit_to_usermode_loop+0x258/0x2f0 arch/x86/entry/common.c:162
prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
syscall_return_slowpath arch/x86/entry/common.c:265 [inline]
do_syscall_64+0x6e5/0x940 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x453da9
RSP: 002b:00007f297546ace8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 000000000072bf80 RCX: 0000000000453da9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000000072bf80
RBP: 000000000072bf80 R08: 0000000000000000 R09: 000000000072bf58
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000a3e8ef R14: 00007f297546b9c0 R15: 0000000000000001
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 syzk...@googlegroups.com.

syzbot will keep track of this bug report.
If you forgot to add the Reported-by tag, once the fix for this bug is
merged
into any tree, please reply to this email with:
#syz fix: exact-commit-title
If you want to test a patch for this bug, please reply with:
#syz test: git://repo/address.git branch
and provide the patch inline or as an attachment.
To mark this as a duplicate of another syzbot report, please reply with:
#syz dup: exact-subject-of-another-report
If it's a one-off invalid bug report, please reply with:
#syz invalid
Note: if the crash happens again, it will cause creation of a new bug
report.
Note: all commands must start from beginning of the line in the email body.

[Xin Long]

It seems that we also need to process the chunks in
outqueue->control_chunk_list in sctp_for_each_tx_datachunk()
when peeling off.

[Dmitry Vyukov]

Hi Xin,

Did you mail any fix for this?
The bug is still open, but the crash did not happen in the past
months. It seems that 3 different bugs accumulated in this bug: there
was a splash of crashes in Feb 2018, then it stopped crashing, then
some crashes in May 2018, probably a different bug, then stopped
happening again, then another splash in Nov 2018, most likely a
different bugs, then it stopped happening again. If we keep it open,
it will continue accumulating more different bugs.

> --
> You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bug...@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/CADvbK_eandMH1aZvKnzdX%3D3xdS0NSo6_NAeCrKasqA9EON4B0A%40mail.gmail.com.
> For more options, visit https://groups.google.com/d/optout.

[Xin Long]

No, I realized it doesn't make difference to add the process for
control_chunk_list in sctp_for_each_tx_datachunk().

> The bug is still open, but the crash did not happen in the past
> months. It seems that 3 different bugs accumulated in this bug: there
> was a splash of crashes in Feb 2018, then it stopped crashing, then
> some crashes in May 2018, probably a different bug, then stopped
> happening again, then another splash in Nov 2018, most likely a
> different bugs, then it stopped happening again. If we keep it open,
> it will continue accumulating more different bugs.

We've had some fixes for peeling off process added in the latest kernel
since then, which could be related. So I think we can close this one now,
and let's see what the new bugs will look like.

Thanks.

[Dmitry Vyukov]

#syz invalid