linux-kernel - Re: [btrfs] 0f80799866: WARNING:at_fs/sysfs/file.c:#sysfs

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Date:   Fri, 22 Oct 2021 00:18:37 +0800
From:   Anand Jain <anand.jain@...cle.com>
To:     dsterba@...e.cz, kernel test robot <oliver.sang@...el.com>,
        0day robot <lkp@...el.com>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...ts.01.org,
        linux-btrfs@...r.kernel.org, dsterba@...e.com
Subject: Re: [btrfs] 0f80799866: WARNING:at_fs/sysfs/file.c:#sysfs_emit



On 22/10/2021 00:06, David Sterba wrote:
> On Thu, Oct 21, 2021 at 09:35:38PM +0800, kernel test robot wrote:
>>
>>
>> Greeting,
>>
>> FYI, we noticed the following commit (built with gcc-9):
>>
>> commit: 0f807998661ecadb74638c18cbaff8785bb46f8d ("[PATCH 1/2] btrfs: sysfs convert scnprintf and snprintf to use sysfs_emit")
>> url: https://github.com/0day-ci/linux/commits/Anand-Jain/provide-fsid-in-sysfs-devinfo/20211019-082356
>> base: https://git.kernel.org/cgit/linux/kernel/git/kdave/linux.git for-next
>>
>> in testcase: boot
>>
>> on test machine: qemu-system-i386 -enable-kvm -cpu SandyBridge -smp 2 -m 4G
> 
> I wonder if it's related to the 32bit host, I don't see any crash.
> 


We are hitting this warning:

int sysfs_emit(char *buf, const char *fmt, ...)
{
         va_list args;
         int len;

         if (WARN(!buf || offset_in_page(buf),   <====
                  "invalid sysfs_emit: buf:%p\n", buf))
                 return 0;
<snip>


The input buf wasn't page-aligned because it wasn't part of the show().