KASAN: use-after-free Write in refcount_warn_saturate

Status: fixed on 2020/11/16 12:12
Subsystems: bluetooth
[Documentation on labels]
Reported-by: syzbot+7dd7f2f77a7a01d1dc14@syzkaller.appspotmail.com
Fix commit: b83764f9220a Bluetooth: Fix kernel oops triggered by hci_adv_monitors_clear()
First crash: 2345d, last: 2186d
Cause bisection: the issue happens on the oldest tested release (bisect log)
Crash: WARNING in sysfs_warn_dup (log)
Repro: C syz .config
  
Fix bisection: fixed by (bisect log) :
commit b83764f9220a4a14525657466f299850bbc98de9
Author: Miao-chen Chou <mcchou@chromium.org>
Date: Tue Jun 30 03:15:00 2020 +0000

  Bluetooth: Fix kernel oops triggered by hci_adv_monitors_clear()

  
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
KASAN: use-after-free Write in refcount_warn_saturate 3 (5) 2020/11/11 13:25
▶ ▼ Fix bisection attempts (5)
Created Duration User Patch Repo Result
2020/09/04 10:55 3h47m bisect fix upstream OK (1) job log
2020/07/26 01:24 33m bisect fix upstream OK (0) job log log
2020/05/28 06:07 27m bisect fix upstream OK (0) job log log
2020/04/28 05:45 21m bisect fix upstream OK (0) job log log
2020/03/29 05:25 19m bisect fix upstream OK (0) job log log

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in instrument_atomic_write include/linux/instrumented.h:71 [inline]
BUG: KASAN: use-after-free in atomic_set include/asm-generic/atomic-instrumented.h:45 [inline]
BUG: KASAN: use-after-free in refcount_set include/linux/refcount.h:136 [inline]
BUG: KASAN: use-after-free in refcount_warn_saturate+0x19/0x1e0 lib/refcount.c:15
Write of size 4 at addr ffff88809bf70018 by task kworker/1:1/23

CPU: 1 PID: 23 Comm: kworker/1:1 Not tainted 5.8.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events do_enable_set
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x18f/0x20d lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xae/0x436 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
 check_memory_region_inline mm/kasan/generic.c:186 [inline]
 check_memory_region+0x13d/0x180 mm/kasan/generic.c:192
 instrument_atomic_write include/linux/instrumented.h:71 [inline]
 atomic_set include/asm-generic/atomic-instrumented.h:45 [inline]
 refcount_set include/linux/refcount.h:136 [inline]
 refcount_warn_saturate+0x19/0x1e0 lib/refcount.c:15
 refcount_sub_and_test include/linux/refcount.h:274 [inline]
 refcount_dec_and_test include/linux/refcount.h:294 [inline]
 kref_put include/linux/kref.h:64 [inline]
 l2cap_chan_put+0x1d3/0x230 net/bluetooth/l2cap_core.c:502
 do_enable_set+0x4f9/0x980 net/bluetooth/6lowpan.c:1083
 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
 kthread+0x3b5/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

Allocated by task 23:
 save_stack+0x1b/0x40 mm/kasan/common.c:48
 set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc.constprop.0+0xc2/0xd0 mm/kasan/common.c:494
 kmem_cache_alloc_trace+0x14f/0x2d0 mm/slab.c:3551
 kmalloc include/linux/slab.h:555 [inline]
 kzalloc include/linux/slab.h:669 [inline]
 l2cap_chan_create+0x40/0x3a0 net/bluetooth/l2cap_core.c:450
 chan_create net/bluetooth/6lowpan.c:648 [inline]
 bt_6lowpan_listen net/bluetooth/6lowpan.c:967 [inline]
 do_enable_set+0x52f/0x980 net/bluetooth/6lowpan.c:1086
 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
 kthread+0x3b5/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

Freed by task 2529:
 save_stack+0x1b/0x40 mm/kasan/common.c:48
 set_track mm/kasan/common.c:56 [inline]
 kasan_set_free_info mm/kasan/common.c:316 [inline]
 __kasan_slab_free+0xf5/0x140 mm/kasan/common.c:455
 __cache_free mm/slab.c:3426 [inline]
 kfree+0x103/0x2c0 mm/slab.c:3757
 l2cap_chan_destroy net/bluetooth/l2cap_core.c:488 [inline]
 kref_put include/linux/kref.h:65 [inline]
 l2cap_chan_put+0x1b2/0x230 net/bluetooth/l2cap_core.c:502
 do_enable_set+0x4f9/0x980 net/bluetooth/6lowpan.c:1083
 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
 kthread+0x3b5/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

The buggy address belongs to the object at ffff88809bf70000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 24 bytes inside of
 2048-byte region [ffff88809bf70000, ffff88809bf70800)
The buggy address belongs to the page:
page:ffffea00026fdc00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea00028f9148 ffffea0002440388 ffff8880aa000e00
raw: 0000000000000000 ffff88809bf70000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88809bf6ff00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88809bf6ff80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88809bf70000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff88809bf70080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88809bf70100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2020/08/04 20:35 upstream c0842fbc1b18 80a06902 .config console log report syz C ci-upstream-kasan-gce-selinux-root
2020/02/28 05:25 upstream f8788d86ab28 59b57593 .config console log report syz C ci-upstream-kasan-gce-386
* Struck through repros no longer work on HEAD.