Re: KASAN: use-after-free Read in sha512_ctx_mgr_resubmit

[Eric Biggers]

On Wed, Aug 15, 2018 at 09:00:04AM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    7796916146b8 Merge branch 'x86-cpu-for-linus' of git://git..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=164b1922400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=265bef9882cce8d7
> dashboard link: https://syzkaller.appspot.com/bug?extid=d5455bac3ba1ee9114e5
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=1013478c400000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1349c8aa400000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+d5455bac3ba1ee9114e5@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> ==================================================================
> BUG: KASAN: use-after-free in sha512_ctx_mgr_resubmit.part.3+0x3b1/0x4a0
> arch/x86/crypto/sha512-mb/sha512_mb.c:136
> Read of size 4 at addr ffff8801b0b9e838 by task kworker/0:1/13
> 
> CPU: 0 PID: 13 Comm: kworker/0:1 Not tainted 4.18.0+ #187
> 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+0x242/0x2fe mm/kasan/report.c:412
>  __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
>  sha512_ctx_mgr_resubmit.part.3+0x3b1/0x4a0
> arch/x86/crypto/sha512-mb/sha512_mb.c:136
>  sha512_ctx_mgr_resubmit arch/x86/crypto/sha512-mb/sha512_mb.c:135 [inline]
>  sha512_ctx_mgr_flush+0x5c/0xb0 arch/x86/crypto/sha512-mb/sha512_mb.c:367
>  sha512_mb_flusher+0x27b/0x610 arch/x86/crypto/sha512-mb/sha512_mb.c:939
>  mcryptd_flusher+0x342/0x4b0 crypto/mcryptd.c:208
>  process_one_work+0xc73/0x1ba0 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:413
> 
> Allocated by task 23902:
>  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/0x760 mm/slab.c:3727
>  kmalloc include/linux/slab.h:518 [inline]
>  sock_kmalloc+0x156/0x1f0 net/core/sock.c:1996
>  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:1600
>  __do_sys_accept4 net/socket.c:1635 [inline]
>  __se_sys_accept4 net/socket.c:1632 [inline]
>  __x64_sys_accept4+0x97/0xf0 net/socket.c:1632
>  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> Freed by task 23902:
>  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
>  __sock_kfree_s net/core/sock.c:2017 [inline]
>  sock_kfree_s+0x29/0x60 net/core/sock.c:2023
>  hash_sock_destruct+0x157/0x1c0 crypto/algif_hash.c:427
>  __sk_destruct+0x107/0xa60 net/core/sock.c:1573
>  sk_destruct+0x78/0x90 net/core/sock.c:1608
>  __sk_free+0xcf/0x300 net/core/sock.c:1619
>  sk_free+0x42/0x50 net/core/sock.c:1630
>  sock_put include/net/sock.h:1667 [inline]
>  af_alg_release+0x6e/0x90 crypto/af_alg.c:126
>  __sock_release+0xd7/0x260 net/socket.c:600
>  sock_close+0x19/0x20 net/socket.c:1151
>  __fput+0x355/0x8b0 fs/file_table.c:209
>  ____fput+0x15/0x20 fs/file_table.c:243
>  task_work_run+0x1e8/0x2a0 kernel/task_work.c:113
>  tracehook_notify_resume include/linux/tracehook.h:192 [inline]
>  exit_to_usermode_loop+0x313/0x370 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 ffff8801b0b9e340
>  which belongs to the cache kmalloc-2048 of size 2048
> The buggy address is located 1272 bytes inside of
>  2048-byte region [ffff8801b0b9e340, ffff8801b0b9eb40)
> The buggy address belongs to the page:
> page:ffffea0006c2e780 count:1 mapcount:0 mapping:ffff8801dac00c40 index:0x0
> compound_mapcount: 0
> flags: 0x2fffc0000008100(slab|head)
> raw: 02fffc0000008100 ffffea0007543a88 ffffea000760b188 ffff8801dac00c40
> raw: 0000000000000000 ffff8801b0b9e340 0000000100000003 0000000000000000
> page dumped because: kasan: bad access detected
> 
> Memory state around the buggy address:
>  ffff8801b0b9e700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff8801b0b9e780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > ffff8801b0b9e800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                                         ^
>  ffff8801b0b9e880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff8801b0b9e900: 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@xxxxxxxxxxxxxxxxx
> 
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
> syzbot.
> syzbot can test patches for this bug, for details see:
> https://goo.gl/tpsmEJ#testing-patches
> 

The "fix" for this is queued in cryptodev:

#syz fix: crypto: x86 - remove SHA multibuffer routines and mcryptd

- Eric