Subject: KASAN: use-after-free Read in j1939_session_deactivate

From: syzbot <[email-masked]>
Date: Fri, 08 Nov 2019 09:04:12 -0800

Hello,

syzbot found the following crash on:

HEAD commit:    847120f8 Merge branch 'for-linus' of git://git.kernel.org/..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11077272e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8c5e2eca3f31f9bf
dashboard link: https://syzkaller.appspot.com/bug?extid=a47537d3964ef6c874e1
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
userspace arch: i386
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=164973b4e00000

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

vcan0: j1939_xtp_rx_abort_one: 0x0000000017fc679a: 0x00000: (2) System  
resources were needed for another task so this connection managed session  
was terminated.
vcan0: j1939_tp_rxtimer: 0x000000000eaf12e4: abort rx timeout. Force  
session deactivation
==================================================================
BUG: KASAN: use-after-free in j1939_session_deactivate+0x80/0x90  
net/can/j1939/transport.c:1033
Read of size 8 at addr ffff88809958dc00 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_deactivate+0x80/0x90 net/can/j1939/transport.c:1033
  j1939_session_deactivate_activate_next+0x17/0x50  
net/can/j1939/transport.c:1041
  j1939_tp_rxtimer+0xc8/0x27b net/can/j1939/transport.c:1150
  __run_hrtimer kernel/time/hrtimer.c:1514 [inline]
  __hrtimer_run_queues+0x364/0xe40 kernel/time/hrtimer.c:1576
  hrtimer_run_softirq+0x17e/0x270 kernel/time/hrtimer.c:1593
  __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 9265:
  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_session_new+0x81/0x3f0 net/can/j1939/transport.c:1384
  j1939_tp_send+0x249/0x750 net/can/j1939/transport.c:1846
  j1939_sk_send_loop net/can/j1939/socket.c:995 [inline]
  j1939_sk_sendmsg+0xb76/0x1450 net/can/j1939/socket.c:1100
  sock_sendmsg_nosec net/socket.c:637 [inline]
  sock_sendmsg+0xd7/0x130 net/socket.c:657
  ___sys_sendmsg+0x803/0x920 net/socket.c:2311
  __sys_sendmsg+0x105/0x1d0 net/socket.c:2356
  __compat_sys_sendmsg net/compat.c:642 [inline]
  __do_compat_sys_sendmsg net/compat.c:649 [inline]
  __se_compat_sys_sendmsg net/compat.c:646 [inline]
  __ia32_compat_sys_sendmsg+0x7a/0xb0 net/compat.c:646
  do_syscall_32_irqs_on arch/x86/entry/common.c:333 [inline]
  do_fast_syscall_32+0x27b/0xdb3 arch/x86/entry/common.c:404
  entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139

Freed by task 9:
  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_session_destroy net/can/j1939/transport.c:272 [inline]
  __j1939_session_release net/can/j1939/transport.c:280 [inline]
  kref_put include/linux/kref.h:65 [inline]
  j1939_session_put+0x134/0x180 net/can/j1939/transport.c:285
  j1939_session_deactivate_locked net/can/j1939/transport.c:1021 [inline]
  j1939_session_deactivate_locked+0x245/0x2f0 net/can/j1939/transport.c:1009
  j1939_session_deactivate+0x3d/0x90 net/can/j1939/transport.c:1032
  j1939_session_deactivate_activate_next+0x17/0x50  
net/can/j1939/transport.c:1041
  j1939_tp_rxtimer+0xc8/0x27b net/can/j1939/transport.c:1150
  __run_hrtimer kernel/time/hrtimer.c:1514 [inline]
  __hrtimer_run_queues+0x364/0xe40 kernel/time/hrtimer.c:1576
  hrtimer_run_softirq+0x17e/0x270 kernel/time/hrtimer.c:1593
  __do_softirq+0x262/0x98c kernel/softirq.c:292

The buggy address belongs to the object at ffff88809958dc00
  which belongs to the cache kmalloc-512 of size 512
The buggy address is located 0 bytes inside of
  512-byte region [ffff88809958dc00, ffff88809958de00)
The buggy address belongs to the page:
page:ffffea0002656340 refcount:1 mapcount:0 mapping:ffff8880aa400a80  
index:0x0
flags: 0x1fffc0000000200(slab)
raw: 01fffc0000000200 ffffea00028faa88 ffffea0002a31c48 ffff8880aa400a80
raw: 0000000000000000 ffff88809958d000 0000000100000004 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff88809958db00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff88809958db80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff88809958dc00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                    ^
  ffff88809958dc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff88809958dd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

---
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