Subject: KASAN: use-after-free Write in j1939_sock_pending_del

From: syzbot <[email-masked]>
Date: Mon, 04 Nov 2019 21:32:08 -0800

Hello,

syzbot found the following crash on:

HEAD commit:    a99d8080 Linux 5.4-rc6
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=169c59b2e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=896c87b73c6fcda6
dashboard link: https://syzkaller.appspot.com/bug?extid=07bb74aeafc88ba7d5b4
compiler:       clang version 9.0.0 (/home/glider/llvm/clang  
80fee25776c2fb61e74c1ecb1a523375c2500b69)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16fd7044e00000

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

vcan0: j1939_xtp_rx_abort_one: 0x00000000b4d8b78c: 0x00000: (2) System  
resources were needed for another task so this connection managed session  
was terminated.
vcan0: j1939_xtp_rx_abort_one: 0x00000000dadb7e22: 0x00000: (2) System  
resources were needed for another task so this connection managed session  
was terminated.
==================================================================
BUG: KASAN: use-after-free in atomic_sub_return  
include/asm-generic/atomic-instrumented.h:159 [inline]
BUG: KASAN: use-after-free in atomic_dec_return  
include/linux/atomic-fallback.h:455 [inline]
BUG: KASAN: use-after-free in j1939_sock_pending_del+0x20/0x70  
net/can/j1939/socket.c:73
Write of size 4 at addr ffff8880a4a2e4c0 by task ksoftirqd/1/16

CPU: 1 PID: 16 Comm: ksoftirqd/1 Not tainted 5.4.0-rc6 #0
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+0x1d8/0x2f8 lib/dump_stack.c:113
  print_address_description+0x75/0x5c0 mm/kasan/report.c:374
  __kasan_report+0x14b/0x1c0 mm/kasan/report.c:506
  kasan_report+0x26/0x50 mm/kasan/common.c:634
  check_memory_region_inline mm/kasan/generic.c:182 [inline]
  check_memory_region+0x2cf/0x2e0 mm/kasan/generic.c:192
  __kasan_check_write+0x14/0x20 mm/kasan/common.c:98
  atomic_sub_return include/asm-generic/atomic-instrumented.h:159 [inline]
  atomic_dec_return include/linux/atomic-fallback.h:455 [inline]
  j1939_sock_pending_del+0x20/0x70 net/can/j1939/socket.c:73
  __j1939_session_drop net/can/j1939/transport.c:257 [inline]
  j1939_session_destroy net/can/j1939/transport.c:270 [inline]
  __j1939_session_release net/can/j1939/transport.c:280 [inline]
  kref_put include/linux/kref.h:65 [inline]
  j1939_session_put+0xd2/0x150 net/can/j1939/transport.c:285
  j1939_xtp_rx_abort_one+0xd3/0x3f0 net/can/j1939/transport.c:1261
  j1939_xtp_rx_abort net/can/j1939/transport.c:1269 [inline]
  j1939_tp_cmd_recv net/can/j1939/transport.c:1940 [inline]
  j1939_tp_recv+0x633/0xb80 net/can/j1939/transport.c:1973
  j1939_can_recv+0x424/0x650 net/can/j1939/main.c:100
  deliver net/can/af_can.c:568 [inline]
  can_rcv_filter+0x3c0/0x8b0 net/can/af_can.c:602
  can_receive+0x2ac/0x3b0 net/can/af_can.c:659
  can_rcv+0xe4/0x220 net/can/af_can.c:685
  __netif_receive_skb_one_core net/core/dev.c:4929 [inline]
  __netif_receive_skb+0x136/0x370 net/core/dev.c:5043
  process_backlog+0x4d8/0x930 net/core/dev.c:5874
  napi_poll net/core/dev.c:6311 [inline]
  net_rx_action+0x5ef/0x10d0 net/core/dev.c:6379
  __do_softirq+0x333/0x7c4 arch/x86/include/asm/paravirt.h:766
  run_ksoftirqd+0x64/0xf0 kernel/softirq.c:603
  smpboot_thread_fn+0x5b3/0x9a0 kernel/smpboot.c:165
  kthread+0x332/0x350 kernel/kthread.c:255
  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

Allocated by task 8435:
  save_stack mm/kasan/common.c:69 [inline]
  set_track mm/kasan/common.c:77 [inline]
  __kasan_kmalloc+0x11c/0x1b0 mm/kasan/common.c:510
  kasan_kmalloc+0x9/0x10 mm/kasan/common.c:524
  __do_kmalloc mm/slab.c:3655 [inline]
  __kmalloc+0x254/0x340 mm/slab.c:3664
  kmalloc include/linux/slab.h:561 [inline]
  sk_prot_alloc+0xb0/0x290 net/core/sock.c:1605
  sk_alloc+0x38/0x950 net/core/sock.c:1659
  can_create+0x1de/0x480 net/can/af_can.c:157
  __sock_create+0x5cc/0x910 net/socket.c:1418
  sock_create net/socket.c:1469 [inline]
  __sys_socket+0xe7/0x2e0 net/socket.c:1511
  __do_sys_socket net/socket.c:1520 [inline]
  __se_sys_socket net/socket.c:1518 [inline]
  __x64_sys_socket+0x7a/0x90 net/socket.c:1518
  do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 16:
  save_stack mm/kasan/common.c:69 [inline]
  set_track mm/kasan/common.c:77 [inline]
  kasan_set_free_info mm/kasan/common.c:332 [inline]
  __kasan_slab_free+0x12a/0x1e0 mm/kasan/common.c:471
  kasan_slab_free+0xe/0x10 mm/kasan/common.c:480
  __cache_free mm/slab.c:3425 [inline]
  kfree+0x115/0x200 mm/slab.c:3756
  sk_prot_free net/core/sock.c:1642 [inline]
  __sk_destruct+0x523/0x620 net/core/sock.c:1726
  sk_destruct net/core/sock.c:1741 [inline]
  __sk_free+0x35d/0x430 net/core/sock.c:1752
  sock_wfree+0x106/0x140 net/core/sock.c:1968
  skb_release_head_state+0x100/0x210 net/core/skbuff.c:652
  skb_release_all net/core/skbuff.c:663 [inline]
  __kfree_skb+0x25/0x170 net/core/skbuff.c:679
  kfree_skb net/core/skbuff.c:697 [inline]
  skb_queue_purge+0x1a6/0x260 net/core/skbuff.c:3078
  j1939_session_destroy net/can/j1939/transport.c:269 [inline]
  __j1939_session_release net/can/j1939/transport.c:280 [inline]
  kref_put include/linux/kref.h:65 [inline]
  j1939_session_put+0x7f/0x150 net/can/j1939/transport.c:285
  j1939_xtp_rx_abort_one+0xd3/0x3f0 net/can/j1939/transport.c:1261
  j1939_xtp_rx_abort net/can/j1939/transport.c:1269 [inline]
  j1939_tp_cmd_recv net/can/j1939/transport.c:1940 [inline]
  j1939_tp_recv+0x633/0xb80 net/can/j1939/transport.c:1973
  j1939_can_recv+0x424/0x650 net/can/j1939/main.c:100
  deliver net/can/af_can.c:568 [inline]
  can_rcv_filter+0x3c0/0x8b0 net/can/af_can.c:602
  can_receive+0x2ac/0x3b0 net/can/af_can.c:659
  can_rcv+0xe4/0x220 net/can/af_can.c:685
  __netif_receive_skb_one_core net/core/dev.c:4929 [inline]
  __netif_receive_skb+0x136/0x370 net/core/dev.c:5043
  process_backlog+0x4d8/0x930 net/core/dev.c:5874
  napi_poll net/core/dev.c:6311 [inline]
  net_rx_action+0x5ef/0x10d0 net/core/dev.c:6379
  __do_softirq+0x333/0x7c4 arch/x86/include/asm/paravirt.h:766

The buggy address belongs to the object at ffff8880a4a2e000
  which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1216 bytes inside of
  2048-byte region [ffff8880a4a2e000, ffff8880a4a2e800)
The buggy address belongs to the page:
page:ffffea0002928b80 refcount:1 mapcount:0 mapping:ffff8880aa400e00  
index:0x0
flags: 0x1fffc0000000200(slab)
raw: 01fffc0000000200 ffffea0002a48588 ffffea0002443f48 ffff8880aa400e00
raw: 0000000000000000 ffff8880a4a2e000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8880a4a2e380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8880a4a2e400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8880a4a2e480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                            ^
  ffff8880a4a2e500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8880a4a2e580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

---
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