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

From: syzbot <[email-masked]>
Date: Tue, 16 Jan 2018 10:29:01 -0800

Hello,

syzkaller hit the following crash on  
ce3c209f6733e2cff9335bb1b2ac847fa823410a
git://git.cmpxchg.org/linux-mmots.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.
Unfortunately, I don't have any reproducer for this bug yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: [email-masked]
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==================================================================
BUG: KASAN: use-after-free in qdisc_pkt_len include/net/sch_generic.h:577  
[inline]
BUG: KASAN: use-after-free in qdisc_qstats_cpu_backlog_inc  
include/net/sch_generic.h:679 [inline]
BUG: KASAN: use-after-free in pfifo_fast_enqueue+0x398/0x420  
net/sched/sch_generic.c:639
Read of size 4 at addr ffff8801bc753be8 by task syz-executor6/4865

CPU: 1 PID: 4865 Comm: syz-executor6 Not tainted 4.15.0-rc7-mm1+ #56
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  <IRQ>
  __dump_stack lib/dump_stack.c:17 [inline]
  dump_stack+0x194/0x257 lib/dump_stack.c:53
  print_address_description+0x73/0x250 mm/kasan/report.c:256
  kasan_report_error mm/kasan/report.c:354 [inline]
  kasan_report+0x23b/0x360 mm/kasan/report.c:412
  __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
  qdisc_pkt_len include/net/sch_generic.h:577 [inline]
  qdisc_qstats_cpu_backlog_inc include/net/sch_generic.h:679 [inline]
  pfifo_fast_enqueue+0x398/0x420 net/sched/sch_generic.c:639
  __dev_xmit_skb net/core/dev.c:3199 [inline]
  __dev_queue_xmit+0xb54/0x2b50 net/core/dev.c:3501
  dev_queue_xmit+0x17/0x20 net/core/dev.c:3566
  neigh_resolve_output+0x5e2/0xa00 net/core/neighbour.c:1350
  neigh_output include/net/neighbour.h:482 [inline]
  ip6_finish_output2+0xb4a/0x23a0 net/ipv6/ip6_output.c:120
  ip6_finish_output+0x698/0xaf0 net/ipv6/ip6_output.c:154
  NF_HOOK_COND include/linux/netfilter.h:277 [inline]
  ip6_output+0x1eb/0x840 net/ipv6/ip6_output.c:171
  dst_output include/net/dst.h:443 [inline]
  NF_HOOK include/linux/netfilter.h:288 [inline]
  mld_sendpack+0x739/0xe70 net/ipv6/mcast.c:1660
  mld_send_cr net/ipv6/mcast.c:1956 [inline]
  mld_ifc_timer_expire+0x3d9/0x770 net/ipv6/mcast.c:2453
  call_timer_fn+0x228/0x820 kernel/time/timer.c:1318
  expire_timers kernel/time/timer.c:1355 [inline]
  __run_timers+0x7ee/0xb70 kernel/time/timer.c:1658
  run_timer_softirq+0x4c/0x70 kernel/time/timer.c:1684
  __do_softirq+0x2d7/0xb85 kernel/softirq.c:285
  invoke_softirq kernel/softirq.c:365 [inline]
  irq_exit+0x1cc/0x200 kernel/softirq.c:405
  exiting_irq arch/x86/include/asm/apic.h:540 [inline]
  smp_apic_timer_interrupt+0x16b/0x700 arch/x86/kernel/apic/apic.c:1052
  apic_timer_interrupt+0xa9/0xb0 arch/x86/entry/entry_64.S:926
  </IRQ>
RIP: 0010:clear_page_erms+0x7/0x10 arch/x86/lib/clear_page_64.S:49
RSP: 0000:ffff8801a76bf6b0 EFLAGS: 00010246 ORIG_RAX: ffffffffffffff11
RAX: 0000000000000000 RBX: dffffc0000000000 RCX: 00000000000007c0
RDX: ffff8801d6d6e200 RSI: 0000160000000000 RDI: ffff88019e85a840
RBP: ffff8801a76bf700 R08: 000000000002f8d0 R09: 0000000000000000
R10: ffffffffffffffe8 R11: 0000000000000000 R12: ffffea00067a0000
R13: 000000000000003a R14: 000000000000001d R15: 000000000000005a
  __do_huge_pmd_anonymous_page mm/huge_memory.c:570 [inline]
  do_huge_pmd_anonymous_page+0x599/0x1b00 mm/huge_memory.c:728
  create_huge_pmd mm/memory.c:3856 [inline]
  __handle_mm_fault+0x1a0c/0x3ce0 mm/memory.c:4060
  handle_mm_fault+0x38f/0x930 mm/memory.c:4126
  __do_page_fault+0x5c9/0xc90 arch/x86/mm/fault.c:1429
  do_page_fault+0xee/0x720 arch/x86/mm/fault.c:1504
  page_fault+0x4c/0x60 arch/x86/entry/entry_64.S:1249
RIP: 0033:0x405a59
RSP: 002b:0000000000a2f900 EFLAGS: 00010246
RAX: 000000002001d000 RBX: 000000000071bea0 RCX: 0000000000000002
RDX: da87a31dca9dcacc RSI: 0000000000000000 RDI: 0000000002261848
RBP: 0000000000000006 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000a2f900 R11: 0000000000000206 R12: fffffffffffffffe
R13: ffffffffffffffff R14: 0000000000000001 R15: 0000000000000001

Allocated by task 4865:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:447
  set_track mm/kasan/kasan.c:459 [inline]
  kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:552
  kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
  kmem_cache_alloc_node+0x144/0x760 mm/slab.c:3631
  __alloc_skb+0xf1/0x780 net/core/skbuff.c:193
  alloc_skb include/linux/skbuff.h:983 [inline]
  alloc_skb_with_frags+0x10d/0x750 net/core/skbuff.c:5151
  sock_alloc_send_pskb+0x787/0x9b0 net/core/sock.c:2088
  sock_alloc_send_skb+0x32/0x40 net/core/sock.c:2105
  mld_newpack+0x39a/0xaf0 net/ipv6/mcast.c:1585
  add_grhead.isra.24+0x29f/0x380 net/ipv6/mcast.c:1691
  add_grec+0xb89/0x10c0 net/ipv6/mcast.c:1822
  mld_send_cr net/ipv6/mcast.c:1948 [inline]
  mld_ifc_timer_expire+0x364/0x770 net/ipv6/mcast.c:2453
  call_timer_fn+0x228/0x820 kernel/time/timer.c:1318
  expire_timers kernel/time/timer.c:1355 [inline]
  __run_timers+0x7ee/0xb70 kernel/time/timer.c:1658
  run_timer_softirq+0x4c/0x70 kernel/time/timer.c:1684
  __do_softirq+0x2d7/0xb85 kernel/softirq.c:285

Freed by task 23:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:447
  set_track mm/kasan/kasan.c:459 [inline]
  __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:520
  kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:527
  __cache_free mm/slab.c:3485 [inline]
  kmem_cache_free+0x86/0x2b0 mm/slab.c:3743
  kfree_skbmem+0x1a1/0x1d0 net/core/skbuff.c:582
  __kfree_skb net/core/skbuff.c:642 [inline]
  kfree_skb+0x165/0x4c0 net/core/skbuff.c:659
  ip_tunnel_xmit+0x709/0x3650 net/ipv4/ip_tunnel.c:796
  __gre_xmit+0x546/0x8b0 net/ipv4/ip_gre.c:461
  erspan_xmit+0x7eb/0x2430 net/ipv4/ip_gre.c:744
  __netdev_start_xmit include/linux/netdevice.h:4046 [inline]
  netdev_start_xmit include/linux/netdevice.h:4055 [inline]
  xmit_one net/core/dev.c:3020 [inline]
  dev_hard_start_xmit+0x24e/0xac0 net/core/dev.c:3036
  sch_direct_xmit+0x40d/0x1140 net/sched/sch_generic.c:327
  qdisc_restart net/sched/sch_generic.c:393 [inline]
  __qdisc_run+0x57d/0x19c0 net/sched/sch_generic.c:401
  __dev_xmit_skb net/core/dev.c:3200 [inline]
  __dev_queue_xmit+0xb62/0x2b50 net/core/dev.c:3501
  dev_queue_xmit+0x17/0x20 net/core/dev.c:3566
  neigh_resolve_output+0x5e2/0xa00 net/core/neighbour.c:1350
  neigh_output include/net/neighbour.h:482 [inline]
  ip6_finish_output2+0xb4a/0x23a0 net/ipv6/ip6_output.c:120
  ip6_finish_output+0x698/0xaf0 net/ipv6/ip6_output.c:154
  NF_HOOK_COND include/linux/netfilter.h:277 [inline]
  ip6_output+0x1eb/0x840 net/ipv6/ip6_output.c:171
  dst_output include/net/dst.h:443 [inline]
  NF_HOOK include/linux/netfilter.h:288 [inline]
  ndisc_send_skb+0xac4/0x1370 net/ipv6/ndisc.c:491
  ndisc_send_ns+0x38a/0x870 net/ipv6/ndisc.c:628
  addrconf_dad_work+0x980/0x12b0 net/ipv6/addrconf.c:3997
  process_one_work+0xbbf/0x1af0 kernel/workqueue.c:2112
  worker_thread+0x223/0x1990 kernel/workqueue.c:2246
  kthread+0x33c/0x400 kernel/kthread.c:238
  ret_from_fork+0x37/0x50 arch/x86/entry/entry_64.S:530

The buggy address belongs to the object at ffff8801bc753bc0
  which belongs to the cache skbuff_head_cache of size 232
The buggy address is located 40 bytes inside of
  232-byte region [ffff8801bc753bc0, ffff8801bc753ca8)
The buggy address belongs to the page:
page:ffffea0006f1d4c0 count:1 mapcount:0 mapping:ffff8801bc753080 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801bc753080 0000000000000000 000000010000000c
raw: ffffea0006f271e0 ffffea0006f270a0 ffff8801d986ccc0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801bc753a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8801bc753b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc
> ffff8801bc753b80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
                                                           ^
  ffff8801bc753c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8801bc753c80: fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc
==================================================================

---
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