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Date:   Thu, 7 Jun 2018 12:17:35 -0700
From:   Eric Biggers <ebiggers3@gmail.com>
To:     syzbot <syzbot+8a608baf8751184ec727@syzkaller.appspotmail.com>
Cc:     davem@davemloft.net, herbert@gondor.apana.org.au,
        linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org,
        syzkaller-bugs@googlegroups.com
Subject: Re: KASAN: slab-out-of-bounds Write in sha256_final
Message-ID: <20180607191735.GB29665@gmail.com>
References: <00000000000079e595056e0d0796@google.com>
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On Thu, Jun 07, 2018 at 06:12:02AM -0700, syzbot wrote:
> Hello,
> 
> syzbot found 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=12cca2af800000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=2e1a31e8576e013a
> dashboard link: https://syzkaller.appspot.com/bug?extid=8a608baf8751184ec727
> 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+8a608baf8751184ec727@syzkaller.appspotmail.com
> 
> ==================================================================
> BUG: KASAN: slab-out-of-bounds in put_unaligned_be32
> include/linux/unaligned/access_ok.h:60 [inline]
> BUG: KASAN: slab-out-of-bounds in sha256_base_finish
> include/crypto/sha256_base.h:124 [inline]
> BUG: KASAN: slab-out-of-bounds in sha256_final+0x303/0x380
> crypto/sha256_generic.c:253
> Write of size 4 at addr ffff8801ce26f060 by task syz-executor1/7811
> 
> CPU: 0 PID: 7811 Comm: syz-executor1 Not tainted 4.17.0+ #88
> 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
>  put_unaligned_be32 include/linux/unaligned/access_ok.h:60 [inline]
>  sha256_base_finish include/crypto/sha256_base.h:124 [inline]
>  sha256_final+0x303/0x380 crypto/sha256_generic.c:253
>  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: 0033:0x455a09
> Code: 1d ba fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 eb b9 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007fc9dbbc5c68 EFLAGS: 00000246 ORIG_RAX: 00000000000000fa
> RAX: ffffffffffffffda RBX: 00007fc9dbbc66d4 RCX: 0000000000455a09
> RDX: 0000000020000080 RSI: 00000000200001c0 RDI: 0000000000000017
> RBP: 000000000072bea0 R08: 0000000020000200 R09: 0000000000000000
> R10: 0000000000000005 R11: 0000000000000246 R12: 00000000ffffffff
> R13: 0000000000000499 R14: 00000000006fbef8 R15: 0000000000000000
> 
> Allocated by task 7811:
>  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 2819:
>  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 ffff8801ce26f040
>  which belongs to the cache kmalloc-32 of size 32
> The buggy address is located 0 bytes to the right of
>  32-byte region [ffff8801ce26f040, ffff8801ce26f060)
> The buggy address belongs to the page:
> page:ffffea0007389bc0 count:1 mapcount:0 mapping:ffff8801ce26f000
> index:0xffff8801ce26ffc1
> flags: 0x2fffc0000000100(slab)
> raw: 02fffc0000000100 ffff8801ce26f000 ffff8801ce26ffc1 000000010000003f
> raw: ffffea000739d360 ffff8801da801248 ffff8801da8001c0 0000000000000000
> page dumped because: kasan: bad access detected
> 
> Memory state around the buggy address:
>  ffff8801ce26ef00: 00 fc fc 00 00 00 00 00 fc fc 00 00 00 00 00 fc
>  ffff8801ce26ef80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> > ffff8801ce26f000: fb fb fb fb fc fc fc fc 00 00 00 00 fc fc fc fc
>                                                        ^
>  ffff8801ce26f080: 05 fc fc fc fc fc fc fc fb fb fb fb fc fc fc fc
>  ffff8801ce26f100: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
> ==================================================================
> 
> 
> ---
> 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.
> 

Duplicate:

#syz dup: KASAN: slab-out-of-bounds Write in sha1_finup

Tentative fix is "[PATCH] dh key: fix rounding up KDF output length".