WARNING in cbq_destroy

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: d96d875e Merge tag 'fixes_for_v5.5-rc8' of git://git.kerne..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=144f7601e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=83c00afca9cf5153
dashboard link: https://syzkaller.appspot.com/bug?extid=63bdb6006961d8c917c6
compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17a1a721e00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11a91a95e00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+63bdb6...@syzkaller.appspotmail.com

netlink: 96 bytes leftover after parsing attributes in process `syz-executor899'.
------------[ cut here ]------------
WARNING: CPU: 1 PID: 8828 at net/sched/sch_cbq.c:1437 cbq_destroy_class net/sched/sch_cbq.c:1437 [inline]
WARNING: CPU: 1 PID: 8828 at net/sched/sch_cbq.c:1437 cbq_destroy+0x324/0x400 net/sched/sch_cbq.c:1471
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 8828 Comm: syz-executor899 Not tainted 5.5.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1fb/0x318 lib/dump_stack.c:118
panic+0x264/0x7a9 kernel/panic.c:221
__warn+0x209/0x210 kernel/panic.c:582
report_bug+0x1b6/0x2f0 lib/bug.c:195
fixup_bug arch/x86/kernel/traps.c:174 [inline]
do_error_trap+0xda/0x440 arch/x86/kernel/traps.c:267
do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:286
invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1027
RIP: 0010:cbq_destroy_class net/sched/sch_cbq.c:1437 [inline]
RIP: 0010:cbq_destroy+0x324/0x400 net/sched/sch_cbq.c:1471
Code: 32 3d fb eb 06 90 e8 db 85 01 fb 49 8d 5f f8 4d 85 ff 49 0f 44 df 48 85 db 74 4b e8 c6 85 01 fb e9 01 ff ff ff e8 bc 85 01 fb <0f> 0b e9 47 ff ff ff 44 89 e9 80 e1 07 80 c1 03 38 c1 0f 8c 1a ff
RSP: 0018:ffffc900078472b0 EFLAGS: 00010293
RAX: ffffffff8674f7c4 RBX: ffff8880a7ef2320 RCX: ffff8880a25a2580
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc90007847308 R08: ffffffff8674f704 R09: fffffbfff13cd120
R10: fffffbfff13cd120 R11: 0000000000000000 R12: ffff8880a7ef22c0
R13: 0000000000000001 R14: dffffc0000000000 R15: 0000000000000000
qdisc_destroy+0x147/0x4c0 net/sched/sch_generic.c:958
qdisc_put+0x83/0xf0 net/sched/sch_generic.c:985
notify_and_destroy net/sched/sch_api.c:995 [inline]
qdisc_graft+0xcc8/0x11f0 net/sched/sch_api.c:1076
tc_modify_qdisc+0xddd/0x1d90 net/sched/sch_api.c:1663
rtnetlink_rcv_msg+0x889/0xd40 net/core/rtnetlink.c:5424
netlink_rcv_skb+0x19e/0x3e0 net/netlink/af_netlink.c:2477
rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:5442
netlink_unicast_kernel net/netlink/af_netlink.c:1302 [inline]
netlink_unicast+0x767/0x920 net/netlink/af_netlink.c:1328
netlink_sendmsg+0xa2c/0xd50 net/netlink/af_netlink.c:1917
sock_sendmsg_nosec net/socket.c:639 [inline]
sock_sendmsg net/socket.c:659 [inline]
kernel_sendmsg+0x109/0x140 net/socket.c:679
sock_no_sendpage+0x100/0x140 net/core/sock.c:2740
kernel_sendpage net/socket.c:3776 [inline]
sock_sendpage+0xd3/0x120 net/socket.c:937
pipe_to_sendpage+0x238/0x320 fs/splice.c:458
splice_from_pipe_feed fs/splice.c:512 [inline]
__splice_from_pipe+0x33d/0x870 fs/splice.c:636
splice_from_pipe fs/splice.c:671 [inline]
generic_splice_sendpage+0x114/0x180 fs/splice.c:844
do_splice_from fs/splice.c:863 [inline]
do_splice fs/splice.c:1170 [inline]
__do_sys_splice fs/splice.c:1447 [inline]
__se_sys_splice+0x719/0x1ac0 fs/splice.c:1427
__x64_sys_splice+0xe5/0x100 fs/splice.c:1427
do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x446e79
Code: e8 5c b3 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 0b 08 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fa4f9aa3d88 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
RAX: ffffffffffffffda RBX: 00000000006dcc98 RCX: 0000000000446e79
RDX: 0000000000000009 RSI: 0000000000000000 RDI: 0000000000000007
RBP: 00000000006dcc90 R08: 000000000004ffe0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dcc9c
R13: 00000000004aed8e R14: 54c6c2ff093a6d32 R15: 0000000000010000
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

[syzbot]

syzbot has bisected this bug to:

commit d51aae68b142f48232257e96ce317db25445418d
Author: Jiri Pirko <ji...@mellanox.com>
Date: Mon Nov 27 17:37:21 2017 +0000

net: sched: cbq: create block for q->link.block

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=14a51a95e00000
start commit: d96d875e Merge tag 'fixes_for_v5.5-rc8' of git://git.kerne..
git tree: upstream
final crash: https://syzkaller.appspot.com/x/report.txt?x=16a51a95e00000
console output: https://syzkaller.appspot.com/x/log.txt?x=12a51a95e00000

kernel config: https://syzkaller.appspot.com/x/.config?x=83c00afca9cf5153
dashboard link: https://syzkaller.appspot.com/bug?extid=63bdb6006961d8c917c6

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17a1a721e00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11a91a95e00000

Reported-by: syzbot+63bdb6...@syzkaller.appspotmail.com
Fixes: d51aae68b142 ("net: sched: cbq: create block for q->link.block")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger crash:

Reported-and-tested-by: syzbot+63bdb6...@syzkaller.appspotmail.com

Tested on:

commit: 58dd0a81 netfilter: xt_hashlimit: add a quota for each work
git tree: https://github.com/congwang/linux.git syzbot
kernel config: https://syzkaller.appspot.com/x/.config?x=cfbb8fa33f49f9f3

dashboard link: https://syzkaller.appspot.com/bug?extid=63bdb6006961d8c917c6
compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)

Note: testing is done by a robot and is best-effort only.

[Cong Wang]

On Tue, Jan 21, 2020 at 10:57 PM syzbot
<syzbot+63bdb6...@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: d96d875e Merge tag 'fixes_for_v5.5-rc8' of git://git.kerne..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=144f7601e00000
> kernel config: https://syzkaller.appspot.com/x/.config?x=83c00afca9cf5153
> dashboard link: https://syzkaller.appspot.com/bug?extid=63bdb6006961d8c917c6
> compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17a1a721e00000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11a91a95e00000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+63bdb6...@syzkaller.appspotmail.com
>
> netlink: 96 bytes leftover after parsing attributes in process `syz-executor899'.
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 8828 at net/sched/sch_cbq.c:1437 cbq_destroy_class net/sched/sch_cbq.c:1437 [inline]
> WARNING: CPU: 1 PID: 8828 at net/sched/sch_cbq.c:1437 cbq_destroy+0x324/0x400 net/sched/sch_cbq.c:1471

Just FYI: I am still working on a fix, which is more complicated than I thought.

Thanks.

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger crash:

Reported-and-tested-by: syzbot+63bdb6...@syzkaller.appspotmail.com

Tested on:

commit: fa019ae7 net_sched: walk through all child classes of pare..

git tree: https://github.com/congwang/linux.git syzbot
kernel config: https://syzkaller.appspot.com/x/.config?x=cfbb8fa33f49f9f3

dashboard link: https://syzkaller.appspot.com/bug?extid=63bdb6006961d8c917c6
compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)