WARNING in cgroup_exit

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 00c3bc00 Add linux-next specific files for 20190507
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=15220ec8a00000
kernel config: https://syzkaller.appspot.com/x/.config?x=63cd766601c6c9fc
dashboard link: https://syzkaller.appspot.com/bug?extid=f14868630901fc6151d3
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10fcf758a00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1202ffa4a00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+f14868...@syzkaller.appspotmail.com

WARNING: CPU: 0 PID: 8653 at kernel/cgroup/cgroup.c:6008
cgroup_exit+0x51a/0x5d0 kernel/cgroup/cgroup.c:6008
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 8653 Comm: syz-executor076 Not tainted 5.1.0-next-20190507 #2
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+0x172/0x1f0 lib/dump_stack.c:113
panic+0x2cb/0x75a kernel/panic.c:218
__warn.cold+0x20/0x47 kernel/panic.c:575
report_bug+0x263/0x2b0 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:179 [inline]
fixup_bug arch/x86/kernel/traps.c:174 [inline]
do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:272
do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:291
invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:972
RIP: 0010:cgroup_exit+0x51a/0x5d0 kernel/cgroup/cgroup.c:6008
Code: 00 48 c7 c2 20 7f 6d 87 be d3 01 00 00 48 c7 c7 20 80 6d 87 c6 05 01
93 f1 07 01 e8 fb 03 ed ff e9 b1 fb ff ff e8 96 f9 05 00 <0f> 0b e9 75 fc
ff ff e8 8a f9 05 00 48 c7 c2 e0 82 6d 87 be 85 02
RSP: 0018:ffff888086c17a80 EFLAGS: 00010093
RAX: ffff88808e99a000 RBX: 0000000000000001 RCX: ffffffff816b0b5e
RDX: 0000000000000000 RSI: ffffffff816b0eea RDI: 0000000000000001
RBP: ffff888086c17b18 R08: ffff88808e99a000 R09: ffffed1010d82f3e
R10: ffffed1010d82f3d R11: 0000000000000003 R12: ffff88808e99a000
R13: ffff8880981c3200 R14: ffff888086c17af0 R15: 1ffff11010d82f52
do_exit+0x97a/0x2fa0 kernel/exit.c:889
do_group_exit+0x135/0x370 kernel/exit.c:980
get_signal+0x425/0x2270 kernel/signal.c:2638
do_signal+0x87/0x1900 arch/x86/kernel/signal.c:815
exit_to_usermode_loop+0x244/0x2c0 arch/x86/entry/common.c:163
prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
syscall_return_slowpath arch/x86/entry/common.c:276 [inline]
do_syscall_64+0x57e/0x670 arch/x86/entry/common.c:301
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4471e9
Code: e8 3c e6 ff ff 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 ab 06 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f479f748db8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00000000006dcc38 RCX: 00000000004471e9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00000000006dcc38
RBP: 00000000006dcc30 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dcc3c
R13: 00007ffd1ab0c31f R14: 00007f479f7499c0 R15: 0000000000000001
Shutting down cpus with NMI
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
This bug is generated by a bot. It may contain errors.
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syzbot can test patches for this bug, for details see:
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[Roman Gushchin]

Hi!

I'm aware of this problem and presumably know where it comes from. I expect that
https://github.com/rgushchin/linux/commit/b1b6d210789ac0f5d83fd45fdab35eba13cd2ce8
will fix it. I'll post it upstream tomorrow after some additional checks.

Thanks!

Roman

On Tue, May 07, 2019 at 08:36:07PM -0700, syzbot wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: 00c3bc00 Add linux-next specific files for 20190507
> git tree: linux-next

> console output: https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_x_log.txt-3Fx-3D15220ec8a00000&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=jJYgtDM7QT-W-Fz_d29HYQ&m=4iaRvebxGXyCS0fK4EQzBl8b5C4bdRpBidLVWLI_GuM&s=hD1Gj5E63Z0nnx5OQgxeVKb91lJkZHE3qat1sAGP1ZI&e=
> kernel config: https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_x_.config-3Fx-3D63cd766601c6c9fc&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=jJYgtDM7QT-W-Fz_d29HYQ&m=4iaRvebxGXyCS0fK4EQzBl8b5C4bdRpBidLVWLI_GuM&s=_232tg9h9GVIkU_E6zSkqXt_VzdcnBSpy_oTxiER55s&e=
> dashboard link: https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_bug-3Fextid-3Df14868630901fc6151d3&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=jJYgtDM7QT-W-Fz_d29HYQ&m=4iaRvebxGXyCS0fK4EQzBl8b5C4bdRpBidLVWLI_GuM&s=odzDbHDodu7xVLUX5bYH4hZS4TDEJ_Q-Wda-pamijDo&e=

> compiler: gcc (GCC) 9.0.0 20181231 (experimental)

> syz repro: https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_x_repro.syz-3Fx-3D10fcf758a00000&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=jJYgtDM7QT-W-Fz_d29HYQ&m=4iaRvebxGXyCS0fK4EQzBl8b5C4bdRpBidLVWLI_GuM&s=ynJR0QYyNDxBMdGoc8vUawwmdbQQ4uGaH47E1lCToTw&e=
> C reproducer: https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_x_repro.c-3Fx-3D1202ffa4a00000&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=jJYgtDM7QT-W-Fz_d29HYQ&m=4iaRvebxGXyCS0fK4EQzBl8b5C4bdRpBidLVWLI_GuM&s=TOZmN6wU-5eoDmgsf8dUSHVHfd8PiXWMHtLF8zIfVR0&e=

> See https://urldefense.proofpoint.com/v2/url?u=https-3A__goo.gl_tpsmEJ&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=jJYgtDM7QT-W-Fz_d29HYQ&m=4iaRvebxGXyCS0fK4EQzBl8b5C4bdRpBidLVWLI_GuM&s=-w9lCOsM40BNPAQbJETOta_aO2oUunuWHF7_HEF_s4M&e= for more information about syzbot.

> syzbot engineers can be reached at syzk...@googlegroups.com.
>
> syzbot will keep track of this bug report. See:

> https://urldefense.proofpoint.com/v2/url?u=https-3A__goo.gl_tpsmEJ-23status&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=jJYgtDM7QT-W-Fz_d29HYQ&m=4iaRvebxGXyCS0fK4EQzBl8b5C4bdRpBidLVWLI_GuM&s=wbPAdt5WlkacKUJ6S-HTGGEVDOC1zOhIrPgSCdOq3UI&e= for how to communicate with syzbot.

> syzbot can test patches for this bug, for details see:

> https://urldefense.proofpoint.com/v2/url?u=https-3A__goo.gl_tpsmEJ-23testing-2Dpatches&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=jJYgtDM7QT-W-Fz_d29HYQ&m=4iaRvebxGXyCS0fK4EQzBl8b5C4bdRpBidLVWLI_GuM&s=OmC7nK5BIF4c92BuGG7AK2hjFHZhajxJG-VJh0jJRvc&e=

[syzbot]

syzbot has bisected this bug to:

commit e42940e8559c8bbffa8286cc78067c75eb42b374
Author: Stephen Rothwell <s...@canb.auug.org.au>
Date: Tue May 7 01:03:30 2019 +0000

Merge remote-tracking branch 'rdma/for-next'

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1746b4e8a00000
start commit: 00c3bc00 Add linux-next specific files for 20190507
git tree: linux-next
final crash: https://syzkaller.appspot.com/x/report.txt?x=14c6b4e8a00000
console output: https://syzkaller.appspot.com/x/log.txt?x=10c6b4e8a00000

kernel config: https://syzkaller.appspot.com/x/.config?x=63cd766601c6c9fc
dashboard link: https://syzkaller.appspot.com/bug?extid=f14868630901fc6151d3

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10fcf758a00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1202ffa4a00000

Reported-by: syzbot+f14868...@syzkaller.appspotmail.com
Fixes: e42940e8559c ("Merge remote-tracking branch 'rdma/for-next'")

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

[Eric Biggers]

On Wed, May 08, 2019 at 04:19:58AM +0000, Roman Gushchin wrote:
> Hi!
>
> I'm aware of this problem and presumably know where it comes from. I expect that
> https://github.com/rgushchin/linux/commit/b1b6d210789ac0f5d83fd45fdab35eba13cd2ce8
> will fix it. I'll post it upstream tomorrow after some additional checks.
>
> Thanks!
>
> Roman
>

Marking this syzbot report fixed. For future reference, anyone can do this; no
need to wait for someone to do it for you.

#syz fix: cgroup: never call do_group_exit() with task->frozen bit set

- Eric

[Roman Gushchin]

Thank you, Eric!