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

From: syzbot <[email-masked]>
Date: Sun, 11 Nov 2018 21:51:02 -0800

Hello,

syzbot found the following crash on:

HEAD commit:    e12e00e388de Merge tag 'kbuild-fixes-v4.20' of git://git.k..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14cdb6f5400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8f215f21f041a0d7
dashboard link: https://syzkaller.appspot.com/bug?extid=04681da557a0e49a52e5
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)

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: [email-masked]

device bridge_slave_1 left promiscuous mode
bridge0: port 2(bridge_slave_1) entered disabled state
device bridge_slave_0 left promiscuous mode
bridge0: port 1(bridge_slave_0) entered disabled state
==================================================================
BUG: KASAN: use-after-free in nbp_vlan_rcu_free+0x152/0x160  
net/bridge/br_vlan.c:200
Read of size 8 at addr ffff8881bbc44a18 by task swapper/1/0

CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.20.0-rc1+ #332
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+0x244/0x39d lib/dump_stack.c:113
  print_address_description.cold.7+0x9/0x1ff mm/kasan/report.c:256
  kasan_report_error mm/kasan/report.c:354 [inline]
  kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412
  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
  nbp_vlan_rcu_free+0x152/0x160 net/bridge/br_vlan.c:200
  __rcu_reclaim kernel/rcu/rcu.h:240 [inline]
  rcu_do_batch kernel/rcu/tree.c:2437 [inline]
  invoke_rcu_callbacks kernel/rcu/tree.c:2716 [inline]
  rcu_process_callbacks+0x100a/0x1ac0 kernel/rcu/tree.c:2697
  __do_softirq+0x308/0xb7e kernel/softirq.c:292
  invoke_softirq kernel/softirq.c:373 [inline]
  irq_exit+0x17f/0x1c0 kernel/softirq.c:413
  exiting_irq arch/x86/include/asm/apic.h:536 [inline]
  smp_apic_timer_interrupt+0x1cb/0x760 arch/x86/kernel/apic/apic.c:1061
  apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:804
  </IRQ>
RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:57
Code: e9 2c ff ff ff 48 89 c7 48 89 45 d8 e8 d3 43 f3 f9 48 8b 45 d8 e9 ca  
fe ff ff 48 89 df e8 c2 43 f3 f9 eb 82 55 48 89 e5 fb f4 <5d> c3 0f 1f 84  
00 00 00 00 00 55 48 89 e5 f4 5d c3 90 90 90 90 90
RSP: 0018:ffff8881d9b27cb8 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13
RAX: dffffc0000000000 RBX: 1ffff1103b364f9b RCX: 0000000000000000
RDX: 1ffffffff12a3f71 RSI: 0000000000000001 RDI: ffffffff8951fb88
RBP: ffff8881d9b27cb8 R08: ffff8881d9b14340 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8881d9b27d78
R13: ffffffff8a14e1e0 R14: 0000000000000000 R15: 0000000000000001
  arch_safe_halt arch/x86/include/asm/paravirt.h:151 [inline]
  default_idle+0xbf/0x490 arch/x86/kernel/process.c:498
  arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:489
  default_idle_call+0x6d/0x90 kernel/sched/idle.c:93
  cpuidle_idle_call kernel/sched/idle.c:153 [inline]
  do_idle+0x49b/0x5c0 kernel/sched/idle.c:262
  cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:353
  start_secondary+0x487/0x5f0 arch/x86/kernel/smpboot.c:271
  secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

Allocated by task 13858:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
  set_track mm/kasan/kasan.c:460 [inline]
  kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
  kmem_cache_alloc_trace+0x152/0x750 mm/slab.c:3620
  kmalloc include/linux/slab.h:546 [inline]
  kzalloc include/linux/slab.h:741 [inline]
  br_vlan_add+0x6e5/0x1340 net/bridge/br_vlan.c:650
  br_vlan_init+0x339/0x3e0 net/bridge/br_vlan.c:1047
  br_dev_init+0x10d/0x2a0 net/bridge/br_device.c:134
  register_netdevice+0x332/0x11d0 net/core/dev.c:8459
  br_dev_newlink+0x2a/0x130 net/bridge/br_netlink.c:1309
  rtnl_newlink+0xf08/0x1da0 net/core/rtnetlink.c:3175
  rtnetlink_rcv_msg+0x46a/0xc20 net/core/rtnetlink.c:4947
  netlink_rcv_skb+0x172/0x440 net/netlink/af_netlink.c:2477
  rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:4965
  netlink_unicast_kernel net/netlink/af_netlink.c:1310 [inline]
  netlink_unicast+0x5a5/0x760 net/netlink/af_netlink.c:1336
  netlink_sendmsg+0xa18/0xfc0 net/netlink/af_netlink.c:1917
  sock_sendmsg_nosec net/socket.c:621 [inline]
  sock_sendmsg+0xd5/0x120 net/socket.c:631
  ___sys_sendmsg+0x7fd/0x930 net/socket.c:2116
  __sys_sendmsg+0x11d/0x280 net/socket.c:2154
  __do_sys_sendmsg net/socket.c:2163 [inline]
  __se_sys_sendmsg net/socket.c:2161 [inline]
  __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2161
  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 9:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
  set_track mm/kasan/kasan.c:460 [inline]
  __kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
  kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
  __cache_free mm/slab.c:3498 [inline]
  kfree+0xcf/0x230 mm/slab.c:3817
  br_master_vlan_rcu_free+0xa8/0xe0 net/bridge/br_vlan.c:174
  __rcu_reclaim kernel/rcu/rcu.h:240 [inline]
  rcu_do_batch kernel/rcu/tree.c:2437 [inline]
  invoke_rcu_callbacks kernel/rcu/tree.c:2716 [inline]
  rcu_process_callbacks+0x100a/0x1ac0 kernel/rcu/tree.c:2697
  __do_softirq+0x308/0xb7e kernel/softirq.c:292

The buggy address belongs to the object at ffff8881bbc44a00
  which belongs to the cache kmalloc-96 of size 96
The buggy address is located 24 bytes inside of
  96-byte region [ffff8881bbc44a00, ffff8881bbc44a60)
The buggy address belongs to the page:
page:ffffea0006ef1100 count:1 mapcount:0 mapping:ffff8881da8004c0 index:0x0
flags: 0x2fffc0000000200(slab)
raw: 02fffc0000000200 ffffea0007471a08 ffffea000757b908 ffff8881da8004c0
raw: 0000000000000000 ffff8881bbc44000 0000000100000020 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8881bbc44900: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
  ffff8881bbc44980: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
> ffff8881bbc44a00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
                             ^
  ffff8881bbc44a80: 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc
  ffff8881bbc44b00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
==================================================================

---
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