Date:   Tue, 23 Jul 2019 01:49:05 -0700
From:   syzbot <syzbot+701728447042217b67c1@...kaller.appspotmail.com>
To:     linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: KASAN: use-after-free Read in nr_rx_frame (2)

Hello,

syzbot found the following crash on:

HEAD commit:    3bfe1fc4 Merge tag 'for-5.3/dm-changes-2' of git://git.ker..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10413e34600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=21511d77e11db3cb
dashboard link: https://syzkaller.appspot.com/bug?extid=701728447042217b67c1
compiler:       clang version 9.0.0 (/home/glider/llvm/clang  
80fee25776c2fb61e74c1ecb1a523375c2500b69)

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: syzbot+701728447042217b67c1@...kaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in atomic_read  
/./include/asm-generic/atomic-instrumented.h:26 [inline]
BUG: KASAN: use-after-free in refcount_inc_not_zero_checked+0x7c/0x280  
/lib/refcount.c:123
Read of size 4 at addr ffff88808ee52080 by task swapper/1/0

CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.2.0+ #35
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  <IRQ>
  __dump_stack /lib/dump_stack.c:77 [inline]
  dump_stack+0x1d8/0x2f8 /lib/dump_stack.c:113
  print_address_description+0x75/0x5b0 /mm/kasan/report.c:351
  __kasan_report+0x14b/0x1c0 /mm/kasan/report.c:482
  kasan_report+0x26/0x50 /mm/kasan/common.c:612
  check_memory_region_inline /mm/kasan/generic.c:182 [inline]
  check_memory_region+0x2cf/0x2e0 /mm/kasan/generic.c:192
  __kasan_check_read+0x11/0x20 /mm/kasan/common.c:92
  atomic_read /./include/asm-generic/atomic-instrumented.h:26 [inline]
  refcount_inc_not_zero_checked+0x7c/0x280 /lib/refcount.c:123
  refcount_inc_checked+0x15/0x50 /lib/refcount.c:156
  sock_hold /./include/net/sock.h:649 [inline]
  sk_add_node /./include/net/sock.h:701 [inline]
  nr_insert_socket /net/netrom/af_netrom.c:137 [inline]
  nr_rx_frame+0x17bc/0x1e40 /net/netrom/af_netrom.c:1023
  nr_loopback_timer+0x6a/0x140 /net/netrom/nr_loopback.c:59
  call_timer_fn+0xec/0x200 /kernel/time/timer.c:1322
  expire_timers /kernel/time/timer.c:1366 [inline]
  __run_timers+0x7cd/0x9c0 /kernel/time/timer.c:1685
  run_timer_softirq+0x4a/0x90 /kernel/time/timer.c:1698
  __do_softirq+0x333/0x7c4 /./arch/x86/include/asm/paravirt.h:777
  invoke_softirq /kernel/softirq.c:373 [inline]
  irq_exit+0x227/0x230 /kernel/softirq.c:413
  exiting_irq /./arch/x86/include/asm/apic.h:537 [inline]
  smp_apic_timer_interrupt+0x113/0x280 /arch/x86/kernel/apic/apic.c:1095
  apic_timer_interrupt+0xf/0x20 /arch/x86/entry/entry_64.S:828
  </IRQ>
RIP: 0010:native_safe_halt+0xe/0x10 /./arch/x86/include/asm/irqflags.h:61
Code: 06 fa eb ae 89 d9 80 e1 07 80 c1 03 38 c1 7c ba 48 89 df e8 c4 41 06  
fa eb b0 90 90 e9 07 00 00 00 0f 00 2d 76 67 56 00 fb f4 <c3> 90 e9 07 00  
00 00 0f 00 2d 66 67 56 00 f4 c3 90 90 55 48 89 e5
RSP: 0018:ffff8880a98cfd38 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13
RAX: 1ffffffff11950db RBX: ffff8880a98bc340 RCX: dffffc0000000000
RDX: 0000000000000000 RSI: ffffffff812d193a RDI: ffff8880a98bcb78
RBP: ffff8880a98cfd40 R08: ffff8880a98bcb90 R09: ffffed1015317869
R10: ffffed1015317869 R11: 0000000000000000 R12: 0000000000000001
R13: 1ffff11015317868 R14: dffffc0000000000 R15: dffffc0000000000
  arch_cpu_idle+0xa/0x10 /arch/x86/kernel/process.c:571
  default_idle_call+0x59/0xa0 /kernel/sched/idle.c:94
  cpuidle_idle_call /kernel/sched/idle.c:154 [inline]
  do_idle+0x180/0x780 /kernel/sched/idle.c:263
  cpu_startup_entry+0x25/0x30 /kernel/sched/idle.c:354
  start_secondary+0x3f4/0x490 /arch/x86/kernel/smpboot.c:264
  secondary_startup_64+0xa4/0xb0 /arch/x86/kernel/head_64.S:243

Allocated by task 0:
  save_stack /mm/kasan/common.c:69 [inline]
  set_track /mm/kasan/common.c:77 [inline]
  __kasan_kmalloc+0x11c/0x1b0 /mm/kasan/common.c:487
  kasan_kmalloc+0x9/0x10 /mm/kasan/common.c:501
  __do_kmalloc /mm/slab.c:3655 [inline]
  __kmalloc+0x254/0x340 /mm/slab.c:3664
  kmalloc /./include/linux/slab.h:557 [inline]
  sk_prot_alloc+0xb0/0x290 /net/core/sock.c:1603
  sk_alloc+0x38/0x950 /net/core/sock.c:1657
  nr_make_new /net/netrom/af_netrom.c:476 [inline]
  nr_rx_frame+0xabc/0x1e40 /net/netrom/af_netrom.c:959
  nr_loopback_timer+0x6a/0x140 /net/netrom/nr_loopback.c:59
  call_timer_fn+0xec/0x200 /kernel/time/timer.c:1322
  expire_timers /kernel/time/timer.c:1366 [inline]
  __run_timers+0x7cd/0x9c0 /kernel/time/timer.c:1685
  run_timer_softirq+0x4a/0x90 /kernel/time/timer.c:1698
  __do_softirq+0x333/0x7c4 /./arch/x86/include/asm/paravirt.h:777

Freed by task 4044:
  save_stack /mm/kasan/common.c:69 [inline]
  set_track /mm/kasan/common.c:77 [inline]
  __kasan_slab_free+0x12a/0x1e0 /mm/kasan/common.c:449
  kasan_slab_free+0xe/0x10 /mm/kasan/common.c:457
  __cache_free /mm/slab.c:3425 [inline]
  kfree+0x115/0x200 /mm/slab.c:3756
  sk_prot_free /net/core/sock.c:1640 [inline]
  __sk_destruct+0x567/0x660 /net/core/sock.c:1726
  sk_destruct /net/core/sock.c:1734 [inline]
  __sk_free+0x317/0x3e0 /net/core/sock.c:1745
  sk_free /net/core/sock.c:1756 [inline]
  sock_put /./include/net/sock.h:1725 [inline]
  sock_efree+0x60/0x80 /net/core/sock.c:2042
  skb_release_head_state+0x100/0x220 /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+0x6f/0xb0 /net/core/skbuff.c:697
  nr_accept+0x4ef/0x650 /net/netrom/af_netrom.c:819
  __sys_accept4+0x5bc/0x9a0 /net/socket.c:1750
  __do_sys_accept /net/socket.c:1791 [inline]
  __se_sys_accept /net/socket.c:1788 [inline]
  __x64_sys_accept+0x7d/0x90 /net/socket.c:1788
  do_syscall_64+0xfe/0x140 /arch/x86/entry/common.c:296
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff88808ee52000
  which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 128 bytes inside of
  2048-byte region [ffff88808ee52000, ffff88808ee52800)
The buggy address belongs to the page:
page:ffffea00023b9480 refcount:1 mapcount:0 mapping:ffff8880aa400e00  
index:0xffff88808ee53100 compound_mapcount: 0
flags: 0x1fffc0000010200(slab|head)
raw: 01fffc0000010200 ffffea0001732108 ffffea00025f5588 ffff8880aa400e00
raw: ffff88808ee53100 ffff88808ee52000 0000000100000002 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff88808ee51f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff88808ee52000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff88808ee52080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                    ^
  ffff88808ee52100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff88808ee52180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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