KASAN: use-after-free Read in worker_thread (2)

[syzbot]

Hello,

syzkaller hit the following crash on
7dfaa7bc99498da1c6c4a48bee8d2d5265161a8c
git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.

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


==================================================================
BUG: KASAN: use-after-free in worker_thread+0x15bb/0x1990
kernel/workqueue.c:2245
Read of size 8 at addr ffff8801c3a74110 by task kworker/u4:6/3515

CPU: 1 PID: 3515 Comm: kworker/u4:6 Not tainted 4.14.0-rc7+ #112
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
print_address_description+0x73/0x250 mm/kasan/report.c:252
kasan_report_error mm/kasan/report.c:351 [inline]
kasan_report+0x25b/0x340 mm/kasan/report.c:409
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
worker_thread+0x15bb/0x1990 kernel/workqueue.c:2245
kthread+0x35e/0x430 kernel/kthread.c:231
ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:432

Allocated by task 31482:
save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
save_stack+0x43/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
kmem_cache_alloc+0x12e/0x760 mm/slab.c:3562
kmem_cache_zalloc include/linux/slab.h:657 [inline]
kcm_attach net/kcm/kcmsock.c:1394 [inline]
kcm_attach_ioctl net/kcm/kcmsock.c:1460 [inline]
kcm_ioctl+0x2d1/0x1610 net/kcm/kcmsock.c:1695
sock_do_ioctl+0x65/0xb0 net/socket.c:961
sock_ioctl+0x2c2/0x440 net/socket.c:1058
vfs_ioctl fs/ioctl.c:46 [inline]
do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
entry_SYSCALL_64_fastpath+0x1f/0xbe

Freed by task 1249:
save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
save_stack+0x43/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
__cache_free mm/slab.c:3504 [inline]
kmem_cache_free+0x77/0x280 mm/slab.c:3764
unreserve_psock+0x5a1/0x780 net/kcm/kcmsock.c:547
kcm_write_msgs+0xbae/0x1b80 net/kcm/kcmsock.c:590
kcm_tx_work+0x2e/0x190 net/kcm/kcmsock.c:731
process_one_work+0xbf0/0x1bc0 kernel/workqueue.c:2113
worker_thread+0x223/0x1990 kernel/workqueue.c:2247
kthread+0x35e/0x430 kernel/kthread.c:231
ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:432

The buggy address belongs to the object at ffff8801c3a74040
which belongs to the cache kcm_psock_cache of size 552
The buggy address is located 208 bytes inside of
552-byte region [ffff8801c3a74040, ffff8801c3a74268)
The buggy address belongs to the page:
page:ffffea00070e9d00 count:1 mapcount:0 mapping:ffff8801c3a74040 index:0x0
compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801c3a74040 0000000000000000 000000010000000b
raw: ffffea00067920a0 ffff8801d3f39948 ffff8801d3f2a840 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8801c3a74000: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
ffff8801c3a74080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8801c3a74100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8801c3a74180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8801c3a74200: fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc
==================================================================


---
This bug is generated by a dumb bot. It may contain errors.
See https://goo.gl/tpsmEJ for details.
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Please credit me with: Reported-by: syzbot <syzk...@googlegroups.com>

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[Dmitry Vyukov]

On Wed, Nov 8, 2017 at 1:58 PM, syzbot
<bot+bdfa5a20d5d091fffa...@syzkaller.appspotmail.com>
wrote:

> Hello,
>
> syzkaller hit the following crash on
> 7dfaa7bc99498da1c6c4a48bee8d2d5265161a8c
> git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/master
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached
> Raw console output is attached.
>
> Unfortunately, I don't have any reproducer for this bug yet.
>

I guess this is more about kcmsock.c rather than workqueue.c. +kcm maintainers.

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[Cong Wang]

On Wed, Nov 8, 2017 at 5:00 AM, Dmitry Vyukov <dvy...@google.com> wrote:
> On Wed, Nov 8, 2017 at 1:58 PM, syzbot
> <bot+bdfa5a20d5d091fffa...@syzkaller.appspotmail.com>
> wrote:
>> Hello,
>>
>> syzkaller hit the following crash on
>> 7dfaa7bc99498da1c6c4a48bee8d2d5265161a8c
>> git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/master
>> compiler: gcc (GCC) 7.1.1 20170620
>> .config is attached
>> Raw console output is attached.
>>
>> Unfortunately, I don't have any reproducer for this bug yet.
>>
>
>
> I guess this is more about kcmsock.c rather than workqueue.c. +kcm maintainers.

Looks like the work is not cancelled before being freed on this path.
Do you have a C reproducer for me to try?

[syzbot]

syzkaller has found reproducer for the following crash on
d9e0e63d9a6f88440eb201e1491fcf730272c706
git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master

compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.

syzkaller reproducer is attached. See https://goo.gl/kgGztJ
for information about syzkaller reproducers

BUG: KASAN: use-after-free in worker_thread+0x15bb/0x1990

kernel/workqueue.c:2244
Read of size 8 at addr ffff88002d0e3de0 by task kworker/u8:1/1209

CPU: 0 PID: 1209 Comm: kworker/u8:1 Not tainted 4.14.0-rc8-next-20171110+
#12
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011

Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x194/0x257 lib/dump_stack.c:53
print_address_description+0x73/0x250 mm/kasan/report.c:252
kasan_report_error mm/kasan/report.c:351 [inline]
kasan_report+0x25b/0x340 mm/kasan/report.c:409
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430

worker_thread+0x15bb/0x1990 kernel/workqueue.c:2244
kthread+0x37a/0x440 kernel/kthread.c:238
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:437

Allocated by task 11866:

save_stack+0x43/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489

kmem_cache_alloc+0x12e/0x760 mm/slab.c:3548
kmem_cache_zalloc include/linux/slab.h:693 [inline]

kcm_attach net/kcm/kcmsock.c:1394 [inline]
kcm_attach_ioctl net/kcm/kcmsock.c:1460 [inline]
kcm_ioctl+0x2d1/0x1610 net/kcm/kcmsock.c:1695

sock_do_ioctl+0x65/0xb0 net/socket.c:960
sock_ioctl+0x2c2/0x440 net/socket.c:1057
vfs_ioctl fs/ioctl.c:46 [inline]
do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:686

SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692

entry_SYSCALL_64_fastpath+0x1f/0x96

Freed by task 11867:

save_stack+0x43/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524

__cache_free mm/slab.c:3492 [inline]
kmem_cache_free+0x77/0x280 mm/slab.c:3750
kcm_unattach+0xe50/0x1510 net/kcm/kcmsock.c:1563
kcm_unattach_ioctl net/kcm/kcmsock.c:1608 [inline]
kcm_ioctl+0xdf0/0x1610 net/kcm/kcmsock.c:1705
sock_do_ioctl+0x65/0xb0 net/socket.c:960
sock_ioctl+0x2c2/0x440 net/socket.c:1057
vfs_ioctl fs/ioctl.c:46 [inline]
do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:686

SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692

entry_SYSCALL_64_fastpath+0x1f/0x96

The buggy address belongs to the object at ffff88002d0e3d00
which belongs to the cache kcm_psock_cache of size 576
The buggy address is located 224 bytes inside of
576-byte region [ffff88002d0e3d00, ffff88002d0e3f40)

The buggy address belongs to the page:

page:ffffea0000b43880 count:1 mapcount:0 mapping:ffff88002d0e2180 index:0x0
compound_mapcount: 0
flags: 0x100000000008100(slab|head)
raw: 0100000000008100 ffff88002d0e2180 0000000000000000 000000010000000b
raw: ffffea0000b14920 ffffea0000b27e20 ffff88002b0089c0 0000000000000000

page dumped because: kasan: bad access detected

Memory state around the buggy address:

ffff88002d0e3c80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88002d0e3d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff88002d0e3d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88002d0e3e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88002d0e3e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

[Dmitry Vyukov]

On Fri, Nov 10, 2017 at 7:49 PM, Cong Wang <xiyou.w...@gmail.com> wrote:
> On Wed, Nov 8, 2017 at 5:00 AM, Dmitry Vyukov <dvy...@google.com> wrote:
>> On Wed, Nov 8, 2017 at 1:58 PM, syzbot
>> <bot+bdfa5a20d5d091fffa...@syzkaller.appspotmail.com>
>> wrote:
>>> Hello,
>>>
>>> syzkaller hit the following crash on
>>> 7dfaa7bc99498da1c6c4a48bee8d2d5265161a8c
>>> git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/master
>>> compiler: gcc (GCC) 7.1.1 20170620
>>> .config is attached
>>> Raw console output is attached.
>>>
>>> Unfortunately, I don't have any reproducer for this bug yet.
>>>
>>
>>
>> I guess this is more about kcmsock.c rather than workqueue.c. +kcm maintainers.
>
>
> Looks like the work is not cancelled before being freed on this path.
> Do you have a C reproducer for me to try?

This is answered in the email text and the referenced link. If the
wording is not clear, we should improve it.

[Eric Biggers]

No longer occurring, the fix seems to have been commit 7e9964574ee97:

#syz fix: kcm: Only allow TCP sockets to be attached to a KCM mux

- Eric