Message-ID: <000000000000022448056e0fe15d@google.com>
Date:   Thu, 07 Jun 2018 09:36:02 -0700
From:   syzbot <syzbot+d04e58bd384f1fe0b112@...kaller.appspotmail.com>
To:     davem@...emloft.net, herbert@...dor.apana.org.au,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzkaller-bugs@...glegroups.com
Subject: Re: KASAN: slab-out-of-bounds Write in rmd160_final

syzbot has found a reproducer for the following crash on:

HEAD commit:    1c8c5a9d38f6 Merge git://git.kernel.org/pub/scm/linux/kern..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14c7f96f800000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4f1acdf888c9d4e9
dashboard link: https://syzkaller.appspot.com/bug?extid=d04e58bd384f1fe0b112
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=1432a66f800000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11b5034f800000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+d04e58bd384f1fe0b112@...kaller.appspotmail.com

random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
==================================================================
BUG: KASAN: slab-out-of-bounds in rmd160_final+0x201/0x240  
crypto/rmd160.c:334
Write of size 4 at addr ffff8801d88781d8 by task syz-executor724/4532

CPU: 1 PID: 4532 Comm: syz-executor724 Not tainted 4.17.0+ #89
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+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
  rmd160_final+0x201/0x240 crypto/rmd160.c:334
  crypto_shash_final+0x104/0x260 crypto/shash.c:152
  kdf_ctr security/keys/dh.c:186 [inline]
  keyctl_dh_compute_kdf security/keys/dh.c:217 [inline]
  __keyctl_dh_compute+0x1184/0x1bc0 security/keys/dh.c:389
  keyctl_dh_compute+0xb9/0x100 security/keys/dh.c:425
  __do_sys_keyctl security/keys/keyctl.c:1741 [inline]
  __se_sys_keyctl security/keys/keyctl.c:1637 [inline]
  __x64_sys_keyctl+0x12a/0x3b0 security/keys/keyctl.c:1637
  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x43ffa9
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 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 6b 45 00 00 c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffd9be52ed8 EFLAGS: 00000217 ORIG_RAX: 00000000000000fa
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 000000000043ffa9
RDX: 0000000020a53ffb RSI: 0000000020000100 RDI: 0000000000000017
RBP: 00000000006ca018 R08: 0000000020c61fc8 R09: 00000000004002c8
R10: 0000000000000005 R11: 0000000000000217 R12: 00000000004018d0
R13: 0000000000401960 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 4532:
  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]
  keyctl_dh_compute_kdf security/keys/dh.c:211 [inline]
  __keyctl_dh_compute+0xfe9/0x1bc0 security/keys/dh.c:389
  keyctl_dh_compute+0xb9/0x100 security/keys/dh.c:425
  __do_sys_keyctl security/keys/keyctl.c:1741 [inline]
  __se_sys_keyctl security/keys/keyctl.c:1637 [inline]
  __x64_sys_keyctl+0x12a/0x3b0 security/keys/keyctl.c:1637
  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 2865:
  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
  single_release+0x8f/0xb0 fs/seq_file.c:609
  __fput+0x353/0x890 fs/file_table.c:209
  ____fput+0x15/0x20 fs/file_table.c:243
  task_work_run+0x1e4/0x290 kernel/task_work.c:113
  tracehook_notify_resume include/linux/tracehook.h:192 [inline]
  exit_to_usermode_loop+0x2bd/0x310 arch/x86/entry/common.c:166
  prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
  syscall_return_slowpath arch/x86/entry/common.c:265 [inline]
  do_syscall_64+0x6ac/0x800 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8801d88781c0
  which belongs to the cache kmalloc-32 of size 32
The buggy address is located 24 bytes inside of
  32-byte region [ffff8801d88781c0, ffff8801d88781e0)
The buggy address belongs to the page:
page:ffffea0007621e00 count:1 mapcount:0 mapping:ffff8801d8878000  
index:0xffff8801d8878fc1
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801d8878000 ffff8801d8878fc1 0000000100000018
raw: ffffea00070e71e0 ffffea00076222a0 ffff8801da8001c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801d8878080: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
  ffff8801d8878100: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
> ffff8801d8878180: fb fb fb fb fc fc fc fc 00 00 00 fc fc fc fc fc
                                                     ^
  ffff8801d8878200: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
  ffff8801d8878280: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
==================================================================

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