linux-kernel - Re: [syzbot] [damon?] divide error in damon_set

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Message-ID: <d127a181-b734-a6b1-5752-b8597f6adc92@huawei.com>
Date:   Fri, 26 May 2023 20:59:12 +0800
From:   Kefeng Wang <wangkefeng.wang@...wei.com>
To:     syzbot <syzbot+841a46899768ec7bec67@...kaller.appspotmail.com>,
        <akpm@...ux-foundation.org>, <damon@...ts.linux.dev>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        <sj@...nel.org>, <syzkaller-bugs@...glegroups.com>
Subject: Re: [syzbot] [damon?] divide error in damon_set_attrs



On 2023/5/26 19:51, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    44c026a73be8 Linux 6.4-rc3
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=13a92b31280000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=f389ffdf4e9ba3f0
> dashboard link: https://syzkaller.appspot.com/bug?extid=841a46899768ec7bec67
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> userspace arch: i386
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/35f16ee05df7/disk-44c026a7.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/10399498a570/vmlinux-44c026a7.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/5c72201ea4ba/bzImage-44c026a7.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+841a46899768ec7bec67@...kaller.appspotmail.com
> 
> divide error: 0000 [#1] PREEMPT SMP KASAN
> CPU: 1 PID: 13527 Comm: syz-executor.1 Not tainted 6.4.0-rc3-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/28/2023
> RIP: 0010:damon_nr_accesses_to_accesses_bp mm/damon/core.c:491 [inline]
> RIP: 0010:damon_nr_accesses_for_new_attrs mm/damon/core.c:497 [inline]
> RIP: 0010:damon_update_monitoring_result mm/damon/core.c:506 [inline]
> RIP: 0010:damon_update_monitoring_results mm/damon/core.c:534 [inline]
> RIP: 0010:damon_set_attrs+0x224/0x460 mm/damon/core.c:555

make aggr_interval great than or equal sample_interval?

diff --git a/mm/damon/core.c b/mm/damon/core.c
index d9ef62047bf5..6fe1960f3d6b 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -525,8 +525,8 @@ static void damon_update_monitoring_results(struct 
damon_ctx *ctx,

         /* if any interval is zero, simply forgive conversion */
         if (!old_attrs->sample_interval || !old_attrs->aggr_interval ||
-                       !new_attrs->sample_interval ||
-                       !new_attrs->aggr_interval)
+           !new_attrs->sample_interval || !new_attrs->aggr_interval ||
+           new_attrs->aggr_interval < new_attrs->sample_interval)
                 return;