Re: KASAN: use-after-free Read in sha512_mb_flusher

[Tim Chen]

On 08/20/2018 07:46 PM, Eric Biggers wrote:
> On Wed, Aug 15, 2018 at 09:35:03AM -0700, syzbot wrote:
>> Hello,
>>
>> syzbot found the following crash on:
>>
>> HEAD commit:    5ed5da74de9e Add linux-next specific files for 20180813
>> git tree:       linux-next
>> console output: https://syzkaller.appspot.com/x/log.txt?x=13fd82c4400000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=18edf0289d1b5ab
>> dashboard link: https://syzkaller.appspot.com/bug?extid=94ee41ce442afe333d2e
>> 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+94ee41ce442afe333d2e@xxxxxxxxxxxxxxxxxxxxxxxxx
>>
>> RDX: 00000000200002c0 RSI: 0000000000000005 RDI: 0000000000000004
>> RBP: 00000000009300a0 R08: 0000000000000000 R09: 0000000000000000
>> R10: 0000000000000f6a R11: 0000000000000246 R12: 0000000000000006
>> R13: 00000000004d3840 R14: 00000000004c85ae R15: 0000000000000003
>> ==================================================================
>> BUG: KASAN: use-after-free in sha512_mb_flusher+0x572/0x610
>> arch/x86/crypto/sha512-mb/sha512_mb.c:940
>> Read of size 8 at addr ffff8801b35669d8 by task kworker/0:2/1879
>>
>> CPU: 0 PID: 1879 Comm: kworker/0:2 Not tainted 4.18.0-next-20180813+ #37
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
>> Google 01/01/2011
>> Workqueue: crypto mcryptd_flusher
>> Call Trace:
>>  __dump_stack lib/dump_stack.c:77 [inline]
>>  dump_stack+0x1c9/0x2b4 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+0x242/0x30d mm/kasan/report.c:412
>>  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
>>  sha512_mb_flusher+0x572/0x610 arch/x86/crypto/sha512-mb/sha512_mb.c:940
>>  mcryptd_flusher+0x342/0x4b0 crypto/mcryptd.c:208
>>  process_one_work+0xc73/0x1aa0 kernel/workqueue.c:2153
>>  worker_thread+0x189/0x13c0 kernel/workqueue.c:2296
>>  kthread+0x35a/0x420 kernel/kthread.c:246
>>  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:415
>>
>> Allocated by task 18983:
>>  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
>>  __do_kmalloc mm/slab.c:3718 [inline]
>>  __kmalloc+0x14e/0x720 mm/slab.c:3727
>>  kmalloc include/linux/slab.h:518 [inline]
>>  sock_kmalloc+0x156/0x1f0 net/core/sock.c:1983
>>  hash_accept_parent_nokey+0x58/0x2e0 crypto/algif_hash.c:438
>>  hash_accept_parent+0x5b/0x80 crypto/algif_hash.c:465
>>  af_alg_accept+0x127/0x7d0 crypto/af_alg.c:296
>>  alg_accept+0x46/0x60 crypto/af_alg.c:332
>>  __sys_accept4+0x3b2/0x8a0 net/socket.c:1589
>>  __do_sys_accept4 net/socket.c:1624 [inline]
>>  __se_sys_accept4 net/socket.c:1621 [inline]
>>  __x64_sys_accept4+0x97/0xf0 net/socket.c:1621
>>  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
>>
>> Freed by task 18979:
>>  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+0xd9/0x210 mm/slab.c:3813
>>  __sock_kfree_s net/core/sock.c:2004 [inline]
>>  sock_kfree_s+0x29/0x60 net/core/sock.c:2010
>>  hash_sock_destruct+0x157/0x1c0 crypto/algif_hash.c:427
>>  __sk_destruct+0x107/0xa60 net/core/sock.c:1560
>>  sk_destruct+0x78/0x90 net/core/sock.c:1595
>>  __sk_free+0xcf/0x300 net/core/sock.c:1606
>>  sk_free+0x42/0x50 net/core/sock.c:1617
>>  sock_put include/net/sock.h:1691 [inline]
>>  af_alg_release+0x6e/0x90 crypto/af_alg.c:126
>>  __sock_release+0xd7/0x250 net/socket.c:580
>>  sock_close+0x19/0x20 net/socket.c:1140
>>  __fput+0x376/0x8a0 fs/file_table.c:279
>>  ____fput+0x15/0x20 fs/file_table.c:312
>>  task_work_run+0x1e8/0x2a0 kernel/task_work.c:113
>>  tracehook_notify_resume include/linux/tracehook.h:193 [inline]
>>  exit_to_usermode_loop+0x318/0x380 arch/x86/entry/common.c:166
>>  prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
>>  syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
>>  do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293
>>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
>>
>> The buggy address belongs to the object at ffff8801b3566600
>>  which belongs to the cache kmalloc-2048 of size 2048
>> The buggy address is located 984 bytes inside of
>>  2048-byte region [ffff8801b3566600, ffff8801b3566e00)
>> The buggy address belongs to the page:
>> page:ffffea0006cd5980 count:1 mapcount:0 mapping:ffff8801dac00c40 index:0x0
>> compound_mapcount: 0
>> flags: 0x2fffc0000008100(slab|head)
>> raw: 02fffc0000008100 ffffea0006cf2c08 ffffea000764ef08 ffff8801dac00c40
>> raw: 0000000000000000 ffff8801b3566600 0000000100000003 0000000000000000
>> page dumped because: kasan: bad access detected
>>
>> Memory state around the buggy address:
>>  ffff8801b3566880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>  ffff8801b3566900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>> ffff8801b3566980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>                                                     ^
>>  ffff8801b3566a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>  ffff8801b3566a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>> ==================================================================
>>
>>
> 
> This is probably the same root cause as the other sha512_mb use-after-free
> (https://lkml.org/lkml/2018/8/15/296), see my reply there.
> 
> #syz dup: KASAN: use-after-free Read in sha512_ctx_mgr_resubmit
> 
> - Eric
> 

Yes, I think it is similar to the previous report.  Megha is working to debug
it.

Tim