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

From: syzbot <[email-masked]>
Date: Tue, 07 Nov 2017 12:28:24 -0800

Hello,

syzkaller hit the following crash on  
287683d027a3ff83feb6c7044430c79881664ecf
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.

==================================================================
BUG: KASAN: use-after-free in rds_tcp_kill_sock net/rds/tcp.c:530 [inline]
BUG: KASAN: use-after-free in rds_tcp_dev_event+0xc01/0xc90  
net/rds/tcp.c:568
Read of size 8 at addr ffff8801cd879200 by task kworker/u4:3/147

CPU: 0 PID: 147 Comm: kworker/u4:3 Not tainted 4.14.0-rc7+ #156
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: netns cleanup_net
Call Trace:
  __dump_stack lib/dump_stack.c:16 [inline]
  dump_stack+0x194/0x257 lib/dump_stack.c:52
  print_address_description+0x73/0x250 mm/kasan/report.c:252
  kasan_report_error mm/kasan/report.c:351 [inline]
  kasan_report+0x25b/0x340 mm/kasan/report.c:409
  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
  rds_tcp_kill_sock net/rds/tcp.c:530 [inline]
  rds_tcp_dev_event+0xc01/0xc90 net/rds/tcp.c:568
  notifier_call_chain+0x136/0x2c0 kernel/notifier.c:93
  __raw_notifier_call_chain kernel/notifier.c:394 [inline]
  raw_notifier_call_chain+0x2d/0x40 kernel/notifier.c:401
  call_netdevice_notifiers_info+0x51/0x90 net/core/dev.c:1671
  call_netdevice_notifiers net/core/dev.c:1687 [inline]
  netdev_run_todo+0x437/0xca0 net/core/dev.c:7846
  rtnl_unlock+0xe/0x10 net/core/rtnetlink.c:106
  default_device_exit_batch+0x4b4/0x5d0 net/core/dev.c:8664
  ops_exit_list.isra.6+0x100/0x150 net/core/net_namespace.c:145
  cleanup_net+0x5c7/0xb50 net/core/net_namespace.c:483
  process_one_work+0xbf0/0x1bc0 kernel/workqueue.c:2113
  worker_thread+0x223/0x1990 kernel/workqueue.c:2247
  kthread+0x35e/0x430 kernel/kthread.c:231
  ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431

Allocated by task 30987:
  save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
  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:551
  __do_kmalloc_node mm/slab.c:3689 [inline]
  __kmalloc_node_track_caller+0x47/0x70 mm/slab.c:3703
  __kmalloc_reserve.isra.40+0x41/0xd0 net/core/skbuff.c:138
  __alloc_skb+0x13b/0x740 net/core/skbuff.c:206
  alloc_skb include/linux/skbuff.h:976 [inline]
  netlink_dump+0x2ba/0xb90 net/netlink/af_netlink.c:2162
  netlink_recvmsg+0x9b6/0x1300 net/netlink/af_netlink.c:1945
  sock_recvmsg_nosec net/socket.c:806 [inline]
  sock_recvmsg+0xc9/0x110 net/socket.c:813
  SYSC_recvfrom+0x2d6/0x570 net/socket.c:1802
  SyS_recvfrom+0x40/0x50 net/socket.c:1774
  entry_SYSCALL_64_fastpath+0x1f/0xbe

Freed by task 30987:
  save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
  save_stack+0x43/0xd0 mm/kasan/kasan.c:447
  set_track mm/kasan/kasan.c:459 [inline]
  kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
  __cache_free mm/slab.c:3503 [inline]
  kfree+0xca/0x250 mm/slab.c:3820
  skb_free_head+0x74/0xb0 net/core/skbuff.c:554
  skb_release_data+0x58c/0x790 net/core/skbuff.c:574
  skb_release_all+0x4a/0x60 net/core/skbuff.c:631
  __kfree_skb net/core/skbuff.c:645 [inline]
  consume_skb+0x153/0x490 net/core/skbuff.c:705
  skb_free_datagram+0x1a/0xe0 net/core/datagram.c:330
  netlink_recvmsg+0x5c6/0x1300 net/netlink/af_netlink.c:1941
  sock_recvmsg_nosec net/socket.c:806 [inline]
  sock_recvmsg+0xc9/0x110 net/socket.c:813
  SYSC_recvfrom+0x2d6/0x570 net/socket.c:1802
  SyS_recvfrom+0x40/0x50 net/socket.c:1774
  entry_SYSCALL_64_fastpath+0x1f/0xbe

The buggy address belongs to the object at ffff8801cd879200
  which belongs to the cache kmalloc-8192 of size 8192
The buggy address is located 0 bytes inside of
  8192-byte region [ffff8801cd879200, ffff8801cd87b200)
The buggy address belongs to the page:
page:ffffea0007361e00 count:1 mapcount:0 mapping:ffff8801cd879200 index:0x0  
compound_mapcount: 0
flags: 0x200000000008100(slab|head)
raw: 0200000000008100 ffff8801cd879200 0000000000000000 0000000100000001
raw: ffffea0007120720 ffffea0006757420 ffff8801dac02080 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801cd879100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff8801cd879180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff8801cd879200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                    ^
  ffff8801cd879280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8801cd879300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

---
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