Subject: KASAN: use-after-free Read in sk_psock_unlink

From: syzbot <[email-masked]>
Date: Fri, 26 Oct 2018 00:37:01 -0700

Hello,

syzbot found the following crash on:

HEAD commit:    8c60c36d0b8c Add linux-next specific files for 20181019
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=17356dbd400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8b6d7c4c81535e89
dashboard link: https://syzkaller.appspot.com/bug?extid=3acd9f67a6a15766686e
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: [email-masked]

EXT4-fs (loop5): couldn't mount RDWR because of unsupported optional  
features (80)
EXT4-fs (loop5): couldn't mount RDWR because of unsupported optional  
features (80)
input:  as /devices/virtual/input/input21
==================================================================
BUG: KASAN: use-after-free in sk_psock_unlink+0x4d8/0x700  
net/core/sock_map.c:992
Read of size 4 at addr ffff8801b7fc1018 by task syz-executor4/21409

CPU: 0 PID: 21409 Comm: syz-executor4 Not tainted 4.19.0-rc8-next-20181019+  
#98
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+0x244/0x39d lib/dump_stack.c:113
  print_address_description.cold.7+0x9/0x1ff mm/kasan/report.c:256
  kasan_report_error mm/kasan/report.c:354 [inline]
  kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412
  __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
  sk_psock_unlink+0x4d8/0x700 net/core/sock_map.c:992
  tcp_bpf_remove+0xd0/0x130 net/ipv4/tcp_bpf.c:511
  tcp_bpf_close+0x1c6/0x4a0 net/ipv4/tcp_bpf.c:551
  inet_release+0x104/0x1f0 net/ipv4/af_inet.c:428
  __sock_release+0xd7/0x250 net/socket.c:580
  sock_close+0x19/0x20 net/socket.c:1142
  __fput+0x3bc/0xa70 fs/file_table.c:279
  ____fput+0x15/0x20 fs/file_table.c:312
  task_work_run+0x1e8/0x2a0 kernel/task_work.c:113
  get_signal+0x1550/0x1970 kernel/signal.c:2347
  do_signal+0x9c/0x21c0 arch/x86/kernel/signal.c:816
  exit_to_usermode_loop+0x2e5/0x380 arch/x86/entry/common.c:162
  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
RIP: 0033:0x457569
Code: fd b3 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 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fd88965ec78 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: 0000000000280000 RBX: 0000000000000006 RCX: 0000000000457569
RDX: fffffffffffffe6e RSI: 0000000020a88f88 RDI: 0000000000000003
RBP: 000000000072bf00 R08: 0000000020e68000 R09: 0000000000000010
R10: 0000000020000000 R11: 0000000000000246 R12: 00007fd88965f6d4
R13: 00000000004c3915 R14: 00000000004d57c0 R15: 00000000ffffffff

Allocated by task 21423:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
  set_track mm/kasan/kasan.c:460 [inline]
  kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
  kmem_cache_alloc_trace+0x152/0x750 mm/slab.c:3620
  kmalloc include/linux/slab.h:546 [inline]
  kzalloc include/linux/slab.h:741 [inline]
  sock_hash_alloc+0x1eb/0x5a0 net/core/sock_map.c:801
  find_and_alloc_map kernel/bpf/syscall.c:129 [inline]
  map_create+0x3bd/0x1100 kernel/bpf/syscall.c:509
  __do_sys_bpf kernel/bpf/syscall.c:2394 [inline]
  __se_sys_bpf kernel/bpf/syscall.c:2371 [inline]
  __x64_sys_bpf+0x303/0x510 kernel/bpf/syscall.c:2371
  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 10109:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
  set_track mm/kasan/kasan.c:460 [inline]
  __kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
  kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
  __cache_free mm/slab.c:3498 [inline]
  kfree+0xcf/0x230 mm/slab.c:3817
  sock_hash_free+0x450/0x640 net/core/sock_map.c:864
  bpf_map_free_deferred+0xd9/0x110 kernel/bpf/syscall.c:290
  process_one_work+0xc8b/0x1c40 kernel/workqueue.c:2153
  worker_thread+0x17f/0x1390 kernel/workqueue.c:2296
  kthread+0x35a/0x440 kernel/kthread.c:246
  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

The buggy address belongs to the object at ffff8801b7fc1000
  which belongs to the cache kmalloc-512 of size 512
The buggy address is located 24 bytes inside of
  512-byte region [ffff8801b7fc1000, ffff8801b7fc1200)
The buggy address belongs to the page:
page:ffffea0006dff040 count:1 mapcount:0 mapping:ffff8801da800940 index:0x0
flags: 0x2fffc0000000200(slab)
raw: 02fffc0000000200 ffffea0006ee5888 ffffea00071fc6c8 ffff8801da800940
raw: 0000000000000000 ffff8801b7fc1000 0000000100000006 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801b7fc0f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  ffff8801b7fc0f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> ffff8801b7fc1000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                             ^
  ffff8801b7fc1080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8801b7fc1100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

---
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