Subject: KASAN: use-after-free Write in bpf_tcp_close

From: syzbot <[email-masked]>
Date: Sun, 27 May 2018 13:06:02 -0700

Hello,

syzbot found the following crash on:

HEAD commit:    ff4fb475cea8 Merge branch 'btf-uapi-cleanups'
git tree:       bpf-next
console output: https://syzkaller.appspot.com/x/log.txt?x=12b3d577800000
kernel config:  https://syzkaller.appspot.com/x/.config?x=b632d8e2c2ab2c1
dashboard link: https://syzkaller.appspot.com/bug?extid=31025a5f3f7650081204
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=109a2f37800000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=171a727b800000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: [email-masked]

==================================================================
BUG: KASAN: use-after-free in cmpxchg_size  
include/asm-generic/atomic-instrumented.h:355 [inline]
BUG: KASAN: use-after-free in bpf_tcp_close+0x6f5/0xf80  
kernel/bpf/sockmap.c:265
Write of size 8 at addr ffff8801ca277680 by task syz-executor749/9723

CPU: 0 PID: 9723 Comm: syz-executor749 Not tainted 4.17.0-rc4+ #19
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
  check_memory_region_inline mm/kasan/kasan.c:260 [inline]
  check_memory_region+0x13e/0x1b0 mm/kasan/kasan.c:267
  kasan_check_write+0x14/0x20 mm/kasan/kasan.c:278
  cmpxchg_size include/asm-generic/atomic-instrumented.h:355 [inline]
  bpf_tcp_close+0x6f5/0xf80 kernel/bpf/sockmap.c:265
  inet_release+0x104/0x1f0 net/ipv4/af_inet.c:427
  inet6_release+0x50/0x70 net/ipv6/af_inet6.c:459
  sock_release+0x96/0x1b0 net/socket.c:594
  sock_close+0x16/0x20 net/socket.c:1149
  __fput+0x34d/0x890 fs/file_table.c:209
  ____fput+0x15/0x20 fs/file_table.c:243
  task_work_run+0x1e4/0x290 kernel/task_work.c:113
  exit_task_work include/linux/task_work.h:22 [inline]
  do_exit+0x1aee/0x2730 kernel/exit.c:865
  do_group_exit+0x16f/0x430 kernel/exit.c:968
  __do_sys_exit_group kernel/exit.c:979 [inline]
  __se_sys_exit_group kernel/exit.c:977 [inline]
  __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:977
  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x440a59
RSP: 002b:00007ffdadf92488 EFLAGS: 00000206 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000440a59
RDX: 0000000000440a59 RSI: 0000000000000020 RDI: 0000000000000000
RBP: 0000000000000000 R08: 00000000004002c8 R09: 0000000000401ea0
R10: 00000000004002c8 R11: 0000000000000206 R12: 000000000001b5ac
R13: 0000000000401ea0 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 9723:
  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_node mm/slab.c:3682 [inline]
  __kmalloc_node+0x47/0x70 mm/slab.c:3689
  kmalloc_node include/linux/slab.h:554 [inline]
  bpf_map_area_alloc+0x3f/0x90 kernel/bpf/syscall.c:144
  sock_map_alloc+0x376/0x410 kernel/bpf/sockmap.c:1555
  find_and_alloc_map kernel/bpf/syscall.c:126 [inline]
  map_create+0x393/0x1010 kernel/bpf/syscall.c:448
  __do_sys_bpf kernel/bpf/syscall.c:2128 [inline]
  __se_sys_bpf kernel/bpf/syscall.c:2105 [inline]
  __x64_sys_bpf+0x300/0x4f0 kernel/bpf/syscall.c:2105
  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 4521:
  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
  kvfree+0x61/0x70 mm/util.c:440
  bpf_map_area_free+0x15/0x20 kernel/bpf/syscall.c:155
  sock_map_remove_complete kernel/bpf/sockmap.c:1443 [inline]
  sock_map_free+0x408/0x540 kernel/bpf/sockmap.c:1619
  bpf_map_free_deferred+0xba/0xf0 kernel/bpf/syscall.c:259
  process_one_work+0xc1e/0x1b50 kernel/workqueue.c:2145
  worker_thread+0x1cc/0x1440 kernel/workqueue.c:2279
  kthread+0x345/0x410 kernel/kthread.c:238
  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412

The buggy address belongs to the object at ffff8801ca277680
  which belongs to the cache kmalloc-1024 of size 1024
The buggy address is located 0 bytes inside of
  1024-byte region [ffff8801ca277680, ffff8801ca277a80)
The buggy address belongs to the page:
page:ffffea0007289d80 count:1 mapcount:0 mapping:ffff8801ca276000 index:0x0  
compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801ca276000 0000000000000000 0000000100000007
raw: ffffea0006d12b20 ffffea000763bba0 ffff8801da800ac0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801ca277580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff8801ca277600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff8801ca277680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                    ^
  ffff8801ca277700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8801ca277780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

---
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