KASAN: out-of-bounds Read in pebs_update_state

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    e99332e7 gcc-10: mark more functions __init to avoid secti..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16e4a10c100000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8a96cf498e199d8b
dashboard link: https://syzkaller.appspot.com/bug?extid=45862e7027be5d590577
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17bb1714100000

Bisection is inconclusive: the bug happens on the oldest tested release.

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=12e02714100000
final crash:    https://syzkaller.appspot.com/x/report.txt?x=11e02714100000
console output: https://syzkaller.appspot.com/x/log.txt?x=16e02714100000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+45862e7027be5d590577@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
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
==================================================================


---
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this bug, for details see:
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