bpf-next boot error: KASAN: use-after-free Write in call_usermodehelper_exec_work

bpf-next boot error: KASAN: use-after-free Write in call_usermodehelper_exec_work

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    69b450789136 Merge branch 'misc-BPF-improvements'
git tree:       bpf-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1080d1d7800000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e4078980b886800c
dashboard link: https://syzkaller.appspot.com/bug?extid=2c73319c406f1987d156
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+2c73319c406f1987d156@syzkaller.appspotmail.com

kworker/u4:1 (36) used greatest stack depth: 23056 bytes left
cpuidle: using governor menu
ACPI: bus type PCI registered
PCI: Using configuration type 1 for base access
==================================================================
BUG: KASAN: use-after-free in call_usermodehelper_exec_work+0x2d3/0x310  
kernel/umh.c:195
Write of size 4 at addr ffff8801d9202370 by task kworker/u4:2/50

CPU: 0 PID: 50 Comm: kworker/u4:2 Not tainted 4.17.0-rc6+ #32
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: events_unbound call_usermodehelper_exec_work
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x1b9/0x294 lib/dump_stack.c:113
  print_address_description+0x6c/0x20b mm/kasan/report.c:256
  kasan_report_error mm/kasan/report.c:354 [inline]
  kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
  __asan_report_store4_noabort+0x17/0x20 mm/kasan/report.c:437
  call_usermodehelper_exec_work+0x2d3/0x310 kernel/umh.c:195
  process_one_work+0xc1e/0x1b50 kernel/workqueue.c:2145
  worker_thread+0x1cc/0x1440 kernel/workqueue.c:2279
  kthread+0x345/0x410 kernel/kthread.c:240
  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412

Allocated by task 1:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
  set_track mm/kasan/kasan.c:460 [inline]
  kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
  kmem_cache_alloc_trace+0x152/0x780 mm/slab.c:3620
  kmalloc include/linux/slab.h:512 [inline]
  kzalloc include/linux/slab.h:701 [inline]
  call_usermodehelper_setup+0xe8/0x400 kernel/umh.c:382
  kobject_uevent_env+0xb21/0x1110 lib/kobject_uevent.c:608
  kobject_uevent+0x1f/0x30 lib/kobject_uevent.c:636
  kernel_add_sysfs_param kernel/params.c:798 [inline]
  param_sysfs_builtin kernel/params.c:833 [inline]
  param_sysfs_init+0x3f9/0x486 kernel/params.c:954
  do_one_initcall+0x127/0x913 init/main.c:884
  do_initcall_level init/main.c:952 [inline]
  do_initcalls init/main.c:960 [inline]
  do_basic_setup init/main.c:978 [inline]
  kernel_init_freeable+0x49b/0x58e init/main.c:1135
  kernel_init+0x11/0x1b3 init/main.c:1061
  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412

Freed by task 208:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
  set_track mm/kasan/kasan.c:460 [inline]
  __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
  kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
  __cache_free mm/slab.c:3498 [inline]
  kfree+0xd9/0x260 mm/slab.c:3813
  call_usermodehelper_freeinfo kernel/umh.c:45 [inline]
  umh_complete+0x7b/0x90 kernel/umh.c:59
  call_usermodehelper_exec_async+0x6e8/0x9e0 kernel/umh.c:116
  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412

The buggy address belongs to the object at ffff8801d9202300
  which belongs to the cache kmalloc-192 of size 192
The buggy address is located 112 bytes inside of
  192-byte region [ffff8801d9202300, ffff8801d92023c0)
The buggy address belongs to the page:
page:ffffea0007648080 count:1 mapcount:0 mapping:ffff8801d9202000 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801d9202000 0000000000000000 0000000100000010
raw: ffffea0007647f60 ffff8801da801148 ffff8801da800040 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801d9202200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff8801d9202280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff8801d9202300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                              ^
  ffff8801d9202380: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
  ffff8801d9202400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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 syzkaller@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with  
syzbot.

Re: bpf-next boot error: KASAN: use-after-free Write in call_usermodehelper_exec_work

[Dmitry Vyukov]

On Mon, Jun 4, 2018 at 10:21 PM, syzbot
<syzbot+2c73319c406f1987d156@syzkaller.appspotmail.com> wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    69b450789136 Merge branch 'misc-BPF-improvements'
> git tree:       bpf-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=1080d1d7800000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=e4078980b886800c
> dashboard link: https://syzkaller.appspot.com/bug?extid=2c73319c406f1987d156
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
>
> Unfortunately, I don't have any reproducer for this crash yet.
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+2c73319c406f1987d156@syzkaller.appspotmail.com


This crash now happens on every other boot of mainline tree. This
prevents syzbot testing of new code, and just boots machine with
corrupted memory. Were there any recent changes in umh? +Alexei, you
seem to touch it last. Could your change cause this?



> kworker/u4:1 (36) used greatest stack depth: 23056 bytes left
> cpuidle: using governor menu
> ACPI: bus type PCI registered
> PCI: Using configuration type 1 for base access
> ==================================================================
> BUG: KASAN: use-after-free in call_usermodehelper_exec_work+0x2d3/0x310
> kernel/umh.c:195
> Write of size 4 at addr ffff8801d9202370 by task kworker/u4:2/50
>
> CPU: 0 PID: 50 Comm: kworker/u4:2 Not tainted 4.17.0-rc6+ #32
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Workqueue: events_unbound call_usermodehelper_exec_work
> Call Trace:
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x1b9/0x294 lib/dump_stack.c:113
>  print_address_description+0x6c/0x20b mm/kasan/report.c:256
>  kasan_report_error mm/kasan/report.c:354 [inline]
>  kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
>  __asan_report_store4_noabort+0x17/0x20 mm/kasan/report.c:437
>  call_usermodehelper_exec_work+0x2d3/0x310 kernel/umh.c:195
>  process_one_work+0xc1e/0x1b50 kernel/workqueue.c:2145
>  worker_thread+0x1cc/0x1440 kernel/workqueue.c:2279
>  kthread+0x345/0x410 kernel/kthread.c:240
>  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412
>
> Allocated by task 1:
>  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
>  set_track mm/kasan/kasan.c:460 [inline]
>  kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
>  kmem_cache_alloc_trace+0x152/0x780 mm/slab.c:3620
>  kmalloc include/linux/slab.h:512 [inline]
>  kzalloc include/linux/slab.h:701 [inline]
>  call_usermodehelper_setup+0xe8/0x400 kernel/umh.c:382
>  kobject_uevent_env+0xb21/0x1110 lib/kobject_uevent.c:608
>  kobject_uevent+0x1f/0x30 lib/kobject_uevent.c:636
>  kernel_add_sysfs_param kernel/params.c:798 [inline]
>  param_sysfs_builtin kernel/params.c:833 [inline]
>  param_sysfs_init+0x3f9/0x486 kernel/params.c:954
>  do_one_initcall+0x127/0x913 init/main.c:884
>  do_initcall_level init/main.c:952 [inline]
>  do_initcalls init/main.c:960 [inline]
>  do_basic_setup init/main.c:978 [inline]
>  kernel_init_freeable+0x49b/0x58e init/main.c:1135
>  kernel_init+0x11/0x1b3 init/main.c:1061
>  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412
>
> Freed by task 208:
>  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
>  set_track mm/kasan/kasan.c:460 [inline]
>  __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
>  kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
>  __cache_free mm/slab.c:3498 [inline]
>  kfree+0xd9/0x260 mm/slab.c:3813
>  call_usermodehelper_freeinfo kernel/umh.c:45 [inline]
>  umh_complete+0x7b/0x90 kernel/umh.c:59
>  call_usermodehelper_exec_async+0x6e8/0x9e0 kernel/umh.c:116
>  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412
>
> The buggy address belongs to the object at ffff8801d9202300
>  which belongs to the cache kmalloc-192 of size 192
> The buggy address is located 112 bytes inside of
>  192-byte region [ffff8801d9202300, ffff8801d92023c0)
> The buggy address belongs to the page:
> page:ffffea0007648080 count:1 mapcount:0 mapping:ffff8801d9202000 index:0x0
> flags: 0x2fffc0000000100(slab)
> raw: 02fffc0000000100 ffff8801d9202000 0000000000000000 0000000100000010
> raw: ffffea0007647f60 ffff8801da801148 ffff8801da800040 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>  ffff8801d9202200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>  ffff8801d9202280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>                                                              ^
>  ffff8801d9202380: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>  ffff8801d9202400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
>
>
> ---
> 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 syzkaller@googlegroups.com.
>
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
> syzbot.
>
> --
> You received this message because you are subscribed to the Google Groups
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Re: bpf-next boot error: KASAN: use-after-free Write in call_usermodehelper_exec_work

[Alexei Starovoitov]

On Thu, Jun 07, 2018 at 02:19:16PM +0200, Dmitry Vyukov wrote:
> On Mon, Jun 4, 2018 at 10:21 PM, syzbot
> <syzbot+2c73319c406f1987d156@syzkaller.appspotmail.com> wrote:
> > Hello,
> >
> > syzbot found the following crash on:
> >
> > HEAD commit:    69b450789136 Merge branch 'misc-BPF-improvements'
> > git tree:       bpf-next
> > console output: https://syzkaller.appspot.com/x/log.txt?x=1080d1d7800000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=e4078980b886800c
> > dashboard link: https://syzkaller.appspot.com/bug?extid=2c73319c406f1987d156
> > compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> >
> > Unfortunately, I don't have any reproducer for this crash yet.
> >
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+2c73319c406f1987d156@syzkaller.appspotmail.com
> 
> 
> This crash now happens on every other boot of mainline tree. This
> prevents syzbot testing of new code, and just boots machine with
> corrupted memory. Were there any recent changes in umh? +Alexei, you
> seem to touch it last. Could your change cause this?

looking into it. I think I see the issue. Trying to reproduce.

Re: bpf-next boot error: KASAN: use-after-free Write in call_usermodehelper_exec_work

[Luis R. Rodriguez]

On Thu, Jun 07, 2018 at 09:07:01AM -0700, Alexei Starovoitov wrote:
> On Thu, Jun 07, 2018 at 02:19:16PM +0200, Dmitry Vyukov wrote:
> > On Mon, Jun 4, 2018 at 10:21 PM, syzbot
> > <syzbot+2c73319c406f1987d156@syzkaller.appspotmail.com> wrote:
> > > Hello,
> > >
> > > syzbot found the following crash on:
> > >
> > > HEAD commit:    69b450789136 Merge branch 'misc-BPF-improvements'
> > > git tree:       bpf-next
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=1080d1d7800000
> > > kernel config:  https://syzkaller.appspot.com/x/.config?x=e4078980b886800c
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=2c73319c406f1987d156
> > > compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> > >
> > > Unfortunately, I don't have any reproducer for this crash yet.
> > >
> > > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > > Reported-by: syzbot+2c73319c406f1987d156@syzkaller.appspotmail.com
> > 
> > 
> > This crash now happens on every other boot of mainline tree. This
> > prevents syzbot testing of new code, and just boots machine with
> > corrupted memory. Were there any recent changes in umh? +Alexei, you
> > seem to touch it last. Could your change cause this?
> 
> looking into it. I think I see the issue. Trying to reproduce.

And this is why a test driver would be useful ;)

  Luis

Re: bpf-next boot error: KASAN: use-after-free Write in call_usermodehelper_exec_work

[Dmitry Vyukov]

On Thu, Jun 7, 2018 at 8:12 PM, Luis R. Rodriguez <mcgrof@kernel.org> wrote:
>> > <syzbot+2c73319c406f1987d156@syzkaller.appspotmail.com> wrote:
>> > > Hello,
>> > >
>> > > syzbot found the following crash on:
>> > >
>> > > HEAD commit:    69b450789136 Merge branch 'misc-BPF-improvements'
>> > > git tree:       bpf-next
>> > > console output: https://syzkaller.appspot.com/x/log.txt?x=1080d1d7800000
>> > > kernel config:  https://syzkaller.appspot.com/x/.config?x=e4078980b886800c
>> > > dashboard link: https://syzkaller.appspot.com/bug?extid=2c73319c406f1987d156
>> > > compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
>> > >
>> > > Unfortunately, I don't have any reproducer for this crash yet.
>> > >
>> > > IMPORTANT: if you fix the bug, please add the following tag to the commit:
>> > > Reported-by: syzbot+2c73319c406f1987d156@syzkaller.appspotmail.com
>> >
>> >
>> > This crash now happens on every other boot of mainline tree. This
>> > prevents syzbot testing of new code, and just boots machine with
>> > corrupted memory. Were there any recent changes in umh? +Alexei, you
>> > seem to touch it last. Could your change cause this?
>>
>> looking into it. I think I see the issue. Trying to reproduce.
>
> And this is why a test driver would be useful ;)

And also testing everything with KASAN and LOCKDEP ;)