linux-kernel - Re: [PATCH linux-next] genirq: use sysfs

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Message-ID: <9c552d9a-2d46-4069-a9c4-35fab857bfc3@kernel.org>
Date: Mon, 17 Mar 2025 07:12:32 +0100
From: Jiri Slaby <jirislaby@...nel.org>
To: xie.ludan@....com.cn, tglx@...utronix.de
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH linux-next] genirq: use sysfs_emit() instead of
 scnprintf().

On 17. 03. 25, 7:07, Jiri Slaby wrote:
> Hi,
> 
> your e-mail is both multipart and base64 encoded :(. Pls fix up your 
> setup first.
> 
> On 15. 03. 25, 7:17, xie.ludan@....com.cn wrote:
>> From: XieLudan <xie.ludan@....com.cn>
>>
>>
>> Follow the advice in Documentation/filesystems/sysfs.rst:
>>
>> show() should only use sysfs_emit() or sysfs_emit_at() when formatting
>>
>> the value to be returned to user space.
>>
>>
>> Signed-off-by: XieLudan <xie.ludan@....com.cn>
>>
>> ---
>>
>>   kernel/irq/irqdesc.c | 12 ++++++------
>>
>>   1 file changed, 6 insertions(+), 6 deletions(-)
>>
>>
>> diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
>>
>> index 287830739783..8ffe12fe5af6 100644
>>
>> --- a/kernel/irq/irqdesc.c
>>
>> +++ b/kernel/irq/irqdesc.c
>>
>> @@ -257,11 +257,11 @@ static ssize_t per_cpu_count_show(struct kobject 
>> *kobj,
>>
>> for_each_possible_cpu(cpu) {
>>
>> unsigned int c = irq_desc_kstat_cpu(desc, cpu);
>>
>> -ret += scnprintf(buf + ret, PAGE_SIZE - ret, "%s%u", p, c);
>>
>> +ret += sysfs_emit(buf + ret, "%s%u", p, c);
> 
> Well, so the PAGE_SIZE boundary is never checked for this stacking write 
> now, right?

^^^ not really clear what I mean, so:

If you advance buf by ret every time, sysfs_emit() still would only 
check if buf is not written more than "PAGE_SIZE" bytes. But the 
original code performs this proper "PAGE_SIZE - ret" check.

> thanks,

-- 
js
suse labs