Re: KASAN: use-after-free Read in mac80211_hwsim_del_radio

Hi,

01.03.2018, 11:46, "syzbot" [off-list ref]:

Hello,

syzbot hit the following crash on upstream commit
f3afe530d644488a074291da04a69a296ab63046 (Tue Feb 27 22:02:39 2018 +0000)
Merge branch 'fixes-v4.16-rc4' of
git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security

So far this crash happened 4 times on upstream.
Unfortunately, I don't have any reproducer for this crash yet.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.

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==================================================================
BUG: KASAN: use-after-free in strlen+0x85/0xa0 lib/string.c:482
Read of size 1 at addr ffff8801d6c38f40 by task kworker/0:1/23

CPU: 0 PID: 23 Comm: kworker/0:1 Not tainted 4.16.0-rc3+ #332
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: hwsim_wq destroy_radio
Call Trace:
  __dump_stack lib/dump_stack.c:17 [inline]
  dump_stack+0x194/0x24d 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_load1_noabort+0x14/0x20 mm/kasan/report.c:430
  strlen+0x85/0xa0 lib/string.c:482
  strlen include/linux/string.h:267 [inline]
  hwsim_mcast_del_radio drivers/net/wireless/mac80211_hwsim.c:2835 [inline]
  mac80211_hwsim_del_radio+0x168/0x3b0
drivers/net/wireless/mac80211_hwsim.c:2854
  destroy_radio+0x9d/0x100 drivers/net/wireless/mac80211_hwsim.c:3396
  process_one_work+0xc47/0x1bb0 kernel/workqueue.c:2113
  worker_thread+0x223/0x1990 kernel/workqueue.c:2247
  kthread+0x33c/0x400 kernel/kthread.c:238
  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:406

Allocated by task 6226:
  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
  __do_kmalloc mm/slab.c:3705 [inline]
  __kmalloc_track_caller+0x15e/0x760 mm/slab.c:3720
  kvasprintf+0xa9/0x130 lib/kasprintf.c:25
  kvasprintf_const+0x56/0x160 lib/kasprintf.c:49
  kobject_set_name_vargs+0x5b/0x140 lib/kobject.c:263
  dev_set_name+0xb4/0xf0 drivers/base/core.c:1649
  wiphy_new_nm+0x910/0x21d0 net/wireless/core.c:451
  ieee80211_alloc_hw_nm+0x4b4/0x2180 net/mac80211/main.c:531
  mac80211_hwsim_new_radio+0x227/0x2cd0
drivers/net/wireless/mac80211_hwsim.c:2537
  hwsim_new_radio_nl+0x67a/0x8c0 drivers/net/wireless/mac80211_hwsim.c:3213
  genl_family_rcv_msg+0x7b7/0xfb0 net/netlink/genetlink.c:599
  genl_rcv_msg+0xb2/0x140 net/netlink/genetlink.c:624
  netlink_rcv_skb+0x14b/0x380 net/netlink/af_netlink.c:2444
  genl_rcv+0x28/0x40 net/netlink/genetlink.c:635
  netlink_unicast_kernel net/netlink/af_netlink.c:1308 [inline]
  netlink_unicast+0x4c4/0x6b0 net/netlink/af_netlink.c:1334
  netlink_sendmsg+0xa4a/0xe60 net/netlink/af_netlink.c:1897
  sock_sendmsg_nosec net/socket.c:630 [inline]
  sock_sendmsg+0xca/0x110 net/socket.c:640
  ___sys_sendmsg+0x767/0x8b0 net/socket.c:2046
  __sys_sendmsg+0xe5/0x210 net/socket.c:2080
  SYSC_sendmsg net/socket.c:2091 [inline]
  SyS_sendmsg+0x2d/0x50 net/socket.c:2087
  do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 5:
  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]
  kfree+0xd9/0x260 mm/slab.c:3800
  kfree_const+0x31/0x40 mm/util.c:38
  kobject_rename+0x1b3/0x2a0 lib/kobject.c:501
  device_rename+0x147/0x1f0 drivers/base/core.c:2648
  cfg80211_switch_netns+0x1fa/0x470 net/wireless/core.c:192
  cfg80211_pernet_exit+0x93/0xc0 net/wireless/core.c:1336
  ops_exit_list.isra.6+0xae/0x150 net/core/net_namespace.c:142
  cleanup_net+0x6a1/0xcb0 net/core/net_namespace.c:517
  process_one_work+0xc47/0x1bb0 kernel/workqueue.c:2113
  worker_thread+0x223/0x1990 kernel/workqueue.c:2247
  kthread+0x33c/0x400 kernel/kthread.c:238
  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:406

The buggy address belongs to the object at ffff8801d6c38f40
  which belongs to the cache kmalloc-32 of size 32
The buggy address is located 0 bytes inside of
  32-byte region [ffff8801d6c38f40, ffff8801d6c38f60)
The buggy address belongs to the page:
page:ffffea00075b0e00 count:1 mapcount:0 mapping:ffff8801d6c38000
index:0xffff8801d6c38fc1
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801d6c38000 ffff8801d6c38fc1 000000010000003f
raw: ffffea00075b0c20 ffffea00075b0f20 ffff8801dac001c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801d6c38e00: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
  ffff8801d6c38e80: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc

quoted

 ffff8801d6c38f00: 07 fc fc fc fc fc fc fc fb fb fb fb fc fc fc fc

                                            ^
  ffff8801d6c38f80: fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc
  ffff8801d6c39000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

---
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JFI: As a coincidence, I'm converting pernet_operation and hwsim_net_ops are the last
in drivers directory which is not converted. There is also an issue with hwsim_netgroup,
and I sent a fix today:

https://patchwork.ozlabs.org/patch/879748/

Thanks,
Kirill