KASAN: out-of-bounds Read in perf_iommu_stop

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 050272a0 Linux 4.14.177
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=14c5bc3fe00000
kernel config: https://syzkaller.appspot.com/x/.config?x=b24dc669afb42f8b
dashboard link: https://syzkaller.appspot.com/bug?extid=c5b1640b69902dca8fe8
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+c5b164...@syzkaller.appspotmail.com

FAT-fs (loop1): Can't find a valid FAT filesystem
==================================================================
BUG: KASAN: out-of-bounds in perf_iommu_disable_event arch/x86/events/amd/iommu.c:282 [inline]
BUG: KASAN: out-of-bounds in perf_iommu_stop+0x267/0x280 arch/x86/events/amd/iommu.c:339
Read of size 1 at addr ffff8882128f7318 by task syz-executor.1/4376

CPU: 1 PID: 4376 Comm: syz-executor.1 Not tainted 4.14.177-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:17 [inline]
dump_stack+0x13e/0x194 lib/dump_stack.c:58
print_address_description.cold+0x7c/0x1e2 mm/kasan/report.c:252
kasan_report_error mm/kasan/report.c:351 [inline]
kasan_report mm/kasan/report.c:409 [inline]
kasan_report.cold+0xa9/0x2ae mm/kasan/report.c:393
perf_iommu_disable_event arch/x86/events/amd/iommu.c:282 [inline]
perf_iommu_stop+0x267/0x280 arch/x86/events/amd/iommu.c:339
</IRQ>

The buggy address belongs to the page:
page:ffffea00084a3dc0 count:0 mapcount:0 mapping: (null) index:0x0
flags: 0x57ffe0000000000()
raw: 057ffe0000000000 0000000000000000 0000000000000000 00000000ffffffff
raw: 0000000000000000 0000000100000001 0000000000000000 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8882128f7200: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff8882128f7280: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8882128f7300: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
^
ffff8882128f7380: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff8882128f7400: 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00 00
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.