Subject: KASAN: use-after-free Read in j1939_session_get_by_addr_locked

From: syzbot <[email-masked]>
Date: Sun, 10 Nov 2019 14:54:07 -0800

Hello,

syzbot found the following crash on:

HEAD commit:    00aff683 Merge tag 'for-5.4-rc6-tag' of git://git.kernel.o..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=179eb2c2e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8c5e2eca3f31f9bf
dashboard link: https://syzkaller.appspot.com/bug?extid=ca172a0ac477ac90f045
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=144150e2e00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11aaa9fce00000

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

vcan0: j1939_tp_rxtimer: 0x00000000be22d2f7: rx timeout, send abort
vcan0: j1939_xtp_rx_abort_one: 0x00000000be22d2f7: 0x00000: (3) A timeout  
occurred and this is the connection abort to close the session.
vcan0: j1939_tp_rxtimer: 0x00000000f7dc054a: rx timeout, send abort
vcan0: j1939_xtp_rx_abort_one: 0x00000000f7dc054a: 0x00000: (3) A timeout  
occurred and this is the connection abort to close the session.
==================================================================
BUG: KASAN: use-after-free in j1939_session_get_by_addr_locked+0x648/0x680  
net/can/j1939/transport.c:491
Read of size 8 at addr ffff8880937d9058 by task ksoftirqd/0/9

CPU: 0 PID: 9 Comm: ksoftirqd/0 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+0x197/0x210 lib/dump_stack.c:118
  print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
  __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506
  kasan_report+0x12/0x20 mm/kasan/common.c:634
  __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:132
  j1939_session_get_by_addr_locked+0x648/0x680 net/can/j1939/transport.c:491
  j1939_session_get_by_addr+0x47/0x60 net/can/j1939/transport.c:531
  j1939_xtp_rx_abort_one+0x8d/0x100 net/can/j1939/transport.c:1242
  j1939_xtp_rx_abort net/can/j1939/transport.c:1270 [inline]
  j1939_tp_cmd_recv net/can/j1939/transport.c:1958 [inline]
  j1939_tp_recv+0x798/0x9b0 net/can/j1939/transport.c:1991
  j1939_can_recv+0x4bb/0x620 net/can/j1939/main.c:100
  deliver net/can/af_can.c:568 [inline]
  can_rcv_filter+0x292/0x8e0 net/can/af_can.c:602
  can_receive+0x2e7/0x530 net/can/af_can.c:659
  can_rcv+0x133/0x1b0 net/can/af_can.c:685
  __netif_receive_skb_one_core+0x113/0x1a0 net/core/dev.c:4929
  __netif_receive_skb+0x2c/0x1d0 net/core/dev.c:5043
  process_backlog+0x206/0x750 net/core/dev.c:5874
  napi_poll net/core/dev.c:6311 [inline]
  net_rx_action+0x508/0x1120 net/core/dev.c:6379
  __do_softirq+0x262/0x98c kernel/softirq.c:292
  run_ksoftirqd kernel/softirq.c:603 [inline]
  run_ksoftirqd+0x8e/0x110 kernel/softirq.c:595
  smpboot_thread_fn+0x6a3/0xa40 kernel/smpboot.c:165
  kthread+0x361/0x430 kernel/kthread.c:255
  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

Allocated by task 10302:
  save_stack+0x23/0x90 mm/kasan/common.c:69
  set_track mm/kasan/common.c:77 [inline]
  __kasan_kmalloc mm/kasan/common.c:510 [inline]
  __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:483
  kasan_kmalloc+0x9/0x10 mm/kasan/common.c:524
  kmem_cache_alloc_trace+0x158/0x790 mm/slab.c:3550
  kmalloc include/linux/slab.h:556 [inline]
  kzalloc include/linux/slab.h:690 [inline]
  j1939_priv_create net/can/j1939/main.c:122 [inline]
  j1939_netdev_start+0xa4/0x550 net/can/j1939/main.c:251
  j1939_sk_bind+0x65a/0x8e0 net/can/j1939/socket.c:438
  __sys_bind+0x239/0x290 net/socket.c:1647
  __do_sys_bind net/socket.c:1658 [inline]
  __se_sys_bind net/socket.c:1656 [inline]
  __x64_sys_bind+0x73/0xb0 net/socket.c:1656
  do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 10302:
  save_stack+0x23/0x90 mm/kasan/common.c:69
  set_track mm/kasan/common.c:77 [inline]
  kasan_set_free_info mm/kasan/common.c:332 [inline]
  __kasan_slab_free+0x102/0x150 mm/kasan/common.c:471
  kasan_slab_free+0xe/0x10 mm/kasan/common.c:480
  __cache_free mm/slab.c:3425 [inline]
  kfree+0x10a/0x2c0 mm/slab.c:3756
  __j1939_priv_release net/can/j1939/main.c:154 [inline]
  kref_put include/linux/kref.h:65 [inline]
  j1939_priv_put+0x8b/0xb0 net/can/j1939/main.c:159
  j1939_netdev_stop+0x45/0x190 net/can/j1939/main.c:291
  j1939_sk_release+0x3bd/0x5c0 net/can/j1939/socket.c:580
  __sock_release+0xce/0x280 net/socket.c:590
  sock_close+0x1e/0x30 net/socket.c:1268
  __fput+0x2ff/0x890 fs/file_table.c:280
  ____fput+0x16/0x20 fs/file_table.c:313
  task_work_run+0x145/0x1c0 kernel/task_work.c:113
  tracehook_notify_resume include/linux/tracehook.h:188 [inline]
  exit_to_usermode_loop+0x316/0x380 arch/x86/entry/common.c:163
  prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
  syscall_return_slowpath arch/x86/entry/common.c:274 [inline]
  do_syscall_64+0x65f/0x760 arch/x86/entry/common.c:300
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8880937d8000
  which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 4184 bytes inside of
  8192-byte region [ffff8880937d8000, ffff8880937da000)
The buggy address belongs to the page:
page:ffffea00024df600 refcount:1 mapcount:0 mapping:ffff8880aa4021c0  
index:0x0 compound_mapcount: 0
flags: 0x1fffc0000010200(slab|head)
raw: 01fffc0000010200 ffffea0002623308 ffffea0002a31f08 ffff8880aa4021c0
raw: 0000000000000000 ffff8880937d8000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8880937d8f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8880937d8f80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8880937d9000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                     ^
  ffff8880937d9080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8880937d9100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

---
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