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Date:   Tue, 19 Dec 2017 23:48:01 -0800
From:   syzbot 
Subject: KASAN: use-after-free Read in crypto_aead_free_instance


syzkaller hit the following crash on  
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.
C reproducer is attached
syzkaller reproducer is attached. See
for information about syzkaller reproducers

BUG: KASAN: use-after-free in crypto_aead_free_instance+0xc0/0xd0  
Read of size 8 at addr ffff8801c32cf240 by task cryptomgr_test/6646

CPU: 1 PID: 6646 Comm: cryptomgr_test Not tainted 4.15.0-rc3+ #132
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
  crypto_aead_free_instance+0xc0/0xd0 crypto/aead.c:154
  crypto_free_instance+0x6d/0x100 crypto/algapi.c:77
  crypto_destroy_instance+0x3c/0x80 crypto/algapi.c:85
  crypto_alg_put crypto/internal.h:116 [inline]
  crypto_remove_final+0x212/0x370 crypto/algapi.c:331
  crypto_alg_tested+0x445/0x6f0 crypto/algapi.c:320
  cryptomgr_test+0x17/0x30 crypto/algboss.c:226
  kthread+0x37a/0x440 kernel/kthread.c:238
  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:441

Allocated by task 6641:
  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
  kmem_cache_alloc_trace+0x136/0x750 mm/slab.c:3610
  kmalloc include/linux/slab.h:499 [inline]
  kzalloc include/linux/slab.h:688 [inline]
  pcrypt_create_aead crypto/pcrypt.c:291 [inline]
  pcrypt_create+0x137/0x6c0 crypto/pcrypt.c:346
  cryptomgr_probe+0x74/0x240 crypto/algboss.c:75
  kthread+0x37a/0x440 kernel/kthread.c:238
  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:441

Freed by task 3335:
  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:3488 [inline]
  kfree+0xca/0x250 mm/slab.c:3803
  crypto_larval_destroy+0x110/0x150 crypto/api.c:107
  crypto_alg_put crypto/internal.h:116 [inline]
  crypto_larval_kill+0x1e8/0x2e0 crypto/api.c:167
  crypto_alg_mod_lookup+0x178/0x1b0 crypto/api.c:283
  crypto_find_alg crypto/api.c:501 [inline]
  crypto_alloc_tfm+0xf3/0x2f0 crypto/api.c:534
  crypto_alloc_aead+0x2c/0x40 crypto/aead.c:342
  aead_bind+0x70/0x140 crypto/algif_aead.c:482
  alg_bind+0x1ab/0x440 crypto/af_alg.c:179
  SYSC_bind+0x1b4/0x3f0 net/socket.c:1454
  SyS_bind+0x24/0x30 net/socket.c:1440
  do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline]
  do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389
  entry_SYSENTER_compat+0x51/0x60 arch/x86/entry/entry_64_compat.S:125

The buggy address belongs to the object at ffff8801c32cf240
  which belongs to the cache kmalloc-1024 of size 1024
The buggy address is located 0 bytes inside of
  1024-byte region [ffff8801c32cf240, ffff8801c32cf640)
The buggy address belongs to the page:
page:000000004ffd125b count:1 mapcount:0 mapping:000000007c8f03ee index:0x0  
compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801c32ce040 0000000000000000 0000000100000007
raw: ffffea00070b6ca0 ffffea00070b9120 ffff8801db000ac0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801c32cf100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8801c32cf180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8801c32cf200: fb fb fb fb fb fb fb fb fb fb fb fb 00 00 00 00
  ffff8801c32cf280: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  ffff8801c32cf300: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

This bug is generated by a dumb bot. It may contain errors.
See for details.
Direct all questions to
Please credit me with: Reported-by: syzbot <>

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Once a fix for this bug is merged into any tree, reply to this email with:
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Note: if the crash happens again, it will cause creation of a new bug  
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View attachment "config.txt" of type "text/plain" (126475 bytes)

Download attachment "raw.log" of type "application/octet-stream" (29602 bytes)

View attachment "repro.txt" of type "text/plain" (534 bytes)

Download attachment "repro.c" of type "application/octet-stream" (5085 bytes)

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