KASAN: use-after-free Write in hci_conn

KASAN: use-after-free Write in hci_conn_del
Status: upstream: reported syz repro on 2020/08/04 15:45
Reported-by: syzbot+7b1677fecb5976b0a099@syzkaller.appspotmail.com
First crash: 260d, last: 9d07h

Cause bisection: introduced by (bisect log) :
commit 6a3c7f5c87854e948c3c234e5f5e745c7c553722
Author: Nikolay Borisov <nborisov@suse.com>
Date: Thu May 28 08:05:13 2020 +0000

btrfs: don't balance btree inode pages from buffered write path

Crash: BUG: sleeping function called from invalid context in exc_page_fault (log)
Repro: syz .config

similar bugs (2):
Kernel	Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
linux-4.14	KASAN: use-after-free Write in hci_conn_del	syz			2	25d	258d	0/1	upstream: reported syz repro on 2020/08/06 02:37
linux-4.19	KASAN: use-after-free Write in hci_conn_del	syz			2	26d	261d	0/1	upstream: reported syz repro on 2020/08/04 00:48

Patch testing requests:
Created	Duration	User	Patch	Repo	Result
2020/09/07 02:51	11m	anant.thazhemadam@gmail.com		https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master	report log
2020/09/07 02:50	12m	anant.thazhemadam@gmail.com		https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master	report log

Sample crash report:

==================================================================
BUG: KASAN: use-after-free in hci_conn_del+0x64e/0x6a0 net/bluetooth/hci_conn.c:630
Write of size 8 at addr ffff888095178940 by task syz-executor.4/6870

CPU: 1 PID: 6870 Comm: syz-executor.4 Not tainted 5.8.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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
 hci_conn_del+0x64e/0x6a0 net/bluetooth/hci_conn.c:630
 hci_conn_hash_flush+0x189/0x220 net/bluetooth/hci_conn.c:1558
 hci_dev_do_close+0x5c6/0x1080 net/bluetooth/hci_core.c:1770
 hci_unregister_dev+0x1bd/0xe30 net/bluetooth/hci_core.c:3790
 vhci_release+0x70/0xe0 drivers/bluetooth/hci_vhci.c:340
 __fput+0x285/0x920 fs/file_table.c:281
 task_work_run+0xdd/0x190 kernel/task_work.c:135
 exit_task_work include/linux/task_work.h:25 [inline]
 do_exit+0xb7d/0x29f0 kernel/exit.c:806
 do_group_exit+0x125/0x310 kernel/exit.c:903
 __do_sys_exit_group kernel/exit.c:914 [inline]
 __se_sys_exit_group kernel/exit.c:912 [inline]
 __x64_sys_exit_group+0x3a/0x50 kernel/exit.c:912
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45ce79
Code: Bad RIP value.
RSP: 002b:00007ffdb27de548 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000045ce79
RDX: 00000000004168d1 RSI: 00000000016a85f0 RDI: 0000000000000043
RBP: 00000000004c2b1b R08: 000000000000000b R09: 0000000000000000
R10: 0000000002bb8940 R11: 0000000000000246 R12: 000000000000000e
R13: 00007ffdb27de690 R14: 000000000009ed3c R15: 00007ffdb27de6a0

Allocated by task 3902:
 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
 slab_post_alloc_hook mm/slab.h:586 [inline]
 slab_alloc mm/slab.c:3320 [inline]
 kmem_cache_alloc+0x12c/0x3b0 mm/slab.c:3484
 getname_flags.part.0+0x50/0x4f0 fs/namei.c:138
 getname_flags include/linux/audit.h:320 [inline]
 getname+0x8e/0xd0 fs/namei.c:209
 do_sys_openat2+0xf5/0x420 fs/open.c:1168
 do_sys_open fs/open.c:1190 [inline]
 __do_sys_open fs/open.c:1198 [inline]
 __se_sys_open fs/open.c:1194 [inline]
 __x64_sys_open+0x119/0x1c0 fs/open.c:1194
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 3902:
 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]
 kmem_cache_free+0x7f/0x310 mm/slab.c:3694
 putname+0xe1/0x120 fs/namei.c:259
 do_sys_openat2+0x153/0x420 fs/open.c:1183
 do_sys_open fs/open.c:1190 [inline]
 __do_sys_open fs/open.c:1198 [inline]
 __se_sys_open fs/open.c:1194 [inline]
 __x64_sys_open+0x119/0x1c0 fs/open.c:1194
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff888095178840
 which belongs to the cache names_cache of size 4096
The buggy address is located 256 bytes inside of
 4096-byte region [ffff888095178840, ffff888095179840)
The buggy address belongs to the page:
page:ffffea0002545e00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 head:ffffea0002545e00 order:1 compound_mapcount:0
flags: 0xfffe0000010200(slab|head)
raw: 00fffe0000010200 ffffea0002a02888 ffffea0002571c08 ffff88821bc51380
raw: 0000000000000000 ffff888095178840 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888095178800: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
 ffff888095178880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888095178900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                           ^
 ffff888095178980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888095178a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Fix bisection attempts:
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro
ci-upstream-kasan-gce-root	2021/04/12 17:53	upstream	d434405a	ff51e522	.config	log	report	syz
ci-upstream-kasan-gce-root	2021/03/12 06:35	upstream	f78d76e7	ff51e522	.config	log	report	syz
ci-upstream-kasan-gce-root	2021/01/20 06:35	upstream	45dfb8a5	ff51e522	.config	log	report	syz
ci-upstream-kasan-gce-root	2020/12/21 05:03	upstream	e37b12e4	ff51e522	.config	log	report	syz
ci-upstream-kasan-gce-root	2020/11/13 05:45	upstream	585e5b17	ff51e522	.config	log	report	syz
ci-upstream-kasan-gce-root	2020/10/14 02:32	upstream	b5fc7a89	ff51e522	.config	log	report	syz
ci-upstream-kasan-gce-root	2020/09/07 19:29	upstream	f4d51dff	ff51e522	.config	log	report	syz

Crashes (3):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro
ci-upstream-kasan-gce-root	2020/08/08 10:32	upstream	5631c5e0	ff51e522	.config	log	report	syz
ci-upstream-kasan-gce-selinux-root	2020/08/04 06:25	upstream	bcf87687	196277c4	.config	log	report	syz
ci-upstream-linux-next-kasan-gce-root	2020/08/08 00:54	linux-next	01830e6c	cb436c69	.config	log	report	syz