Subject: BUG: unable to handle kernel NULL pointer dereference

From: syzbot <[email-masked]>
Date: Sun, 03 Dec 2017 04:37:01 -0800

Hello,

syzkaller hit the following crash on  
4fbd8d194f06c8a3fd2af1ce560ddb31f7ec8323
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.
C reproducer is attached
syzkaller reproducer is attached. See https://goo.gl/kgGztJ
for information about syzkaller reproducers

==================================================================
BUG: unable to handle kernel NULL pointer dereference at           (null)
IP:           (null)
PGD 1cb5c9067 P4D 1cb5c9067 PUD 1ca471067 PMD 0
Oops: 0010 [#1] SMP KASAN
Dumping ftrace buffer:
    (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 3636 Comm: syzkaller687795 Not tainted 4.15.0-rc1+ #197
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
task: ffff8801c91c42c0 task.stack: ffff8801bf000000
RIP: 0010:          (null)
RSP: 0018:ffff8801bf007960 EFLAGS: 00010292
RAX: ffff8801cabcfd80 RBX: 1ffff10037e00f2d RCX: ffffffff823a6c31
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffff8801bf007968
RBP: ffff8801bf007b00 R08: 0000000000000000 R09: ffff8801c91f2c90
R10: 0000000000000008 R11: ffffed003923e599 R12: dffffc0000000000
R13: ffff8801cabcfda8 R14: ffff8801c9351400 R15: ffff8801c91f2c80
FS:  00007f7ab2d65700(0000) GS:ffff8801db400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 00000001ccbe8000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  sock_recvmsg_nosec net/socket.c:805 [inline]
  sock_recvmsg+0xc9/0x110 net/socket.c:812
  ___sys_recvmsg+0x29b/0x630 net/socket.c:2207
  __sys_recvmsg+0xe2/0x210 net/socket.c:2252
  SYSC_recvmsg net/socket.c:2264 [inline]
  SyS_recvmsg+0x2d/0x50 net/socket.c:2259
  entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x446439
RSP: 002b:00007f7ab2d64d08 EFLAGS: 00000246 ORIG_RAX: 000000000000002f
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000446439
RDX: 0000000000000040 RSI: 00000000207e0000 RDI: 0000000000000004
RBP: 0000000000000000 R08: 00007f7ab2d65700 R09: 00007f7ab2d65700
R10: 00007f7ab2d65700 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffc4419186f R14: 00007f7ab2d659c0 R15: 0000000000000000
Code:  Bad RIP value.
RIP:           (null) RSP: ffff8801bf007960
CR2: 0000000000000000
---[ end trace 1d6cf58a48d5320c ]---
Kernel panic - not syncing: Fatal exception
BUG: KASAN: use-after-free in skcipher_request_set_tfm  
include/crypto/skcipher.h:499 [inline]
BUG: KASAN: use-after-free in crypto_aead_copy_sgl crypto/algif_aead.c:85  
[inline]
BUG: KASAN: use-after-free in _aead_recvmsg crypto/algif_aead.c:210 [inline]
BUG: KASAN: use-after-free in aead_recvmsg+0x1552/0x1970  
crypto/algif_aead.c:313
Read of size 4 at addr ffff8801cabcfd9c by task syzkaller687795/3634

CPU: 1 PID: 3634 Comm: syzkaller687795 Tainted: G      D           
4.15.0-rc1+ #197
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_load4_noabort+0x14/0x20 mm/kasan/report.c:429
  skcipher_request_set_tfm include/crypto/skcipher.h:499 [inline]
  crypto_aead_copy_sgl crypto/algif_aead.c:85 [inline]
  _aead_recvmsg crypto/algif_aead.c:210 [inline]
  aead_recvmsg+0x1552/0x1970 crypto/algif_aead.c:313
  sock_recvmsg_nosec net/socket.c:805 [inline]
  sock_recvmsg+0xc9/0x110 net/socket.c:812
  ___sys_recvmsg+0x29b/0x630 net/socket.c:2207
  __sys_recvmsg+0xe2/0x210 net/socket.c:2252
  SYSC_recvmsg net/socket.c:2264 [inline]
  SyS_recvmsg+0x2d/0x50 net/socket.c:2259
  entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x446439
RSP: 002b:00007f7ab2d64d08 EFLAGS: 00000246 ORIG_RAX: 000000000000002f
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000446439
RDX: 0000000000000040 RSI: 00000000207e0000 RDI: 0000000000000004
RBP: 0000000000000000 R08: 00007f7ab2d65700 R09: 00007f7ab2d65700
R10: 00007f7ab2d65700 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffc4419186f R14: 00007f7ab2d659c0 R15: 0000000000000000

Allocated by task 3442:
  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
  __do_kmalloc mm/slab.c:3711 [inline]
  __kmalloc+0x162/0x760 mm/slab.c:3720
  kmalloc include/linux/slab.h:504 [inline]
  kzalloc include/linux/slab.h:688 [inline]
  crypto_create_tfm+0x82/0x2e0 crypto/api.c:455
  crypto_alloc_tfm+0x10e/0x2f0 crypto/api.c:540
  crypto_alloc_skcipher+0x2c/0x40 crypto/skcipher.c:926
  crypto_get_default_null_skcipher+0x5f/0x80 crypto/crypto_null.c:164
  crypto_get_default_null_skcipher2 include/crypto/null.h:17 [inline]
  aead_bind+0x89/0x140 crypto/algif_aead.c:472
  alg_bind+0x1ab/0x440 crypto/af_alg.c:179
  SYSC_bind+0x1b4/0x3f0 net/socket.c:1475
  SyS_bind+0x24/0x30 net/socket.c:1461
  entry_SYSCALL_64_fastpath+0x1f/0x96

Freed by task 3522:
  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:3491 [inline]
  kfree+0xca/0x250 mm/slab.c:3806
  kzfree+0x28/0x30 mm/slab_common.c:1482
  crypto_destroy_tfm+0x140/0x2e0 crypto/api.c:581
  crypto_free_skcipher include/crypto/skcipher.h:212 [inline]
  crypto_put_default_null_skcipher+0x35/0x60 crypto/crypto_null.c:185
  crypto_put_default_null_skcipher2 include/crypto/null.h:22 [inline]
  aead_sock_destruct+0x13c/0x220 crypto/algif_aead.c:522
  __sk_destruct+0xfd/0x910 net/core/sock.c:1558
  sk_destruct+0x47/0x80 net/core/sock.c:1593
  __sk_free+0x57/0x230 net/core/sock.c:1601
  sk_free+0x2a/0x40 net/core/sock.c:1612
  sock_put include/net/sock.h:1655 [inline]
  af_alg_release+0x5d/0x70 crypto/af_alg.c:126
  sock_release+0x8d/0x1e0 net/socket.c:596
  sock_close+0x16/0x20 net/socket.c:1125
  __fput+0x333/0x7f0 fs/file_table.c:210
  ____fput+0x15/0x20 fs/file_table.c:244
  task_work_run+0x199/0x270 kernel/task_work.c:113
  exit_task_work include/linux/task_work.h:22 [inline]
  do_exit+0x9bb/0x1ae0 kernel/exit.c:865
  do_group_exit+0x149/0x400 kernel/exit.c:968
  SYSC_exit_group kernel/exit.c:979 [inline]
  SyS_exit_group+0x1d/0x20 kernel/exit.c:977
  entry_SYSCALL_64_fastpath+0x1f/0x96

The buggy address belongs to the object at ffff8801cabcfd80
  which belongs to the cache kmalloc-128 of size 128
The buggy address is located 28 bytes inside of
  128-byte region [ffff8801cabcfd80, ffff8801cabcfe00)
The buggy address belongs to the page:
page:ffffea00072af3c0 count:1 mapcount:0 mapping:ffff8801cabcf000 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801cabcf000 0000000000000000 0000000100000015
raw: ffffea00072a6ba0 ffffea0007291c20 ffff8801db000640 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801cabcfc80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
  ffff8801cabcfd00: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
> ffff8801cabcfd80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                             ^
  ffff8801cabcfe00: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
  ffff8801cabcfe80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
==================================================================
Dumping ftrace buffer:
    (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..

---
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Please credit me with: Reported-by: syzbot <[email-masked]>

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