KASAN: out-of-bounds Read in pebs_update

KASAN: out-of-bounds Read in pebs_update_state
Status: fixed on 2020/09/16 22:51
Reported-by: syzbot+45862e7027be5d590577@syzkaller.appspotmail.com
Fix commit: 033724d68642 fbdev: Detect integer underflow at "struct fbcon_ops"->clear_margins.
First crash: 567d, last: 515d

Cause bisection: the issue happens on the oldest tested release (bisect log)
Crash: WARNING in sysfs_warn_dup (log)
Repro: syz .config

Fix bisection: fixed by (bisect log) :
commit 033724d6864245a11f8e04c066002e6ad22b3fd0
Author: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Date: Wed Jul 15 01:51:02 2020 +0000

fbdev: Detect integer underflow at "struct fbcon_ops"->clear_margins.

Sample crash report:

==================================================================
BUG: KASAN: out-of-bounds in pebs_update_adaptive_cfg arch/x86/events/intel/ds.c:991 [inline]
BUG: KASAN: out-of-bounds in pebs_update_state+0xc27/0xc80 arch/x86/events/intel/ds.c:1046
Read of size 8 at addr ffffc90004857428 by task syz-executor.1/8320

CPU: 0 PID: 8320 Comm: syz-executor.1 Not tainted 5.7.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x188/0x20d lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0x5/0x315 mm/kasan/report.c:382
 __kasan_report.cold+0x35/0x4d mm/kasan/report.c:511
 kasan_report+0x33/0x50 mm/kasan/common.c:625
 pebs_update_adaptive_cfg arch/x86/events/intel/ds.c:991 [inline]
 pebs_update_state+0xc27/0xc80 arch/x86/events/intel/ds.c:1046
 </IRQ>


Memory state around the buggy address:
 ffffc90004857300: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc90004857380: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffc90004857400: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
                                     ^
 ffffc90004857480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc90004857500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================

Crashes (1):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	VM info	Title
ci-upstream-kasan-gce-root	2020/05/11 02:59	upstream	e99332e7b4cd	8742a2b9	.config	log	report	syz