linux-kernel - Re: [PATCH] drivers/xen/xenbus: Replace deprecated strcpy in xenbus_transaction

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Message-ID: <2cce7bee-af02-4850-b1a8-b7f2cf3f1efb@suse.com>
Date: Mon, 13 Oct 2025 11:24:15 +0200
From: Jürgen Groß <jgross@...e.com>
To: Jan Beulich <jbeulich@...e.com>
Cc: linux-hardening@...r.kernel.org, xen-devel@...ts.xenproject.org,
 linux-kernel@...r.kernel.org, Stefano Stabellini <sstabellini@...nel.org>,
 Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
 Jason Andryuk <jason.andryuk@....com>,
 "Dr. David Alan Gilbert" <linux@...blig.org>,
 Thorsten Blum <thorsten.blum@...ux.dev>
Subject: Re: [PATCH] drivers/xen/xenbus: Replace deprecated strcpy in
 xenbus_transaction_end

On 13.10.25 10:22, Jan Beulich wrote:
> On 13.10.2025 09:36, Jürgen Groß wrote:
>> On 13.10.25 08:59, Jan Beulich wrote:
>>> On 12.10.2025 21:55, Thorsten Blum wrote:
>>>> --- a/drivers/xen/xenbus/xenbus_xs.c
>>>> +++ b/drivers/xen/xenbus/xenbus_xs.c
>>>> @@ -546,16 +546,13 @@ int xenbus_transaction_start(struct xenbus_transaction *t)
>>>>    EXPORT_SYMBOL_GPL(xenbus_transaction_start);
>>>>    
>>>>    /* End a transaction.
>>>> - * If abandon is true, transaction is discarded instead of committed.
>>>> + * If abort is true, transaction is discarded instead of committed.
>>>>     */
>>>> -int xenbus_transaction_end(struct xenbus_transaction t, int abort)
>>>> +int xenbus_transaction_end(struct xenbus_transaction t, bool abort)
>>>>    {
>>>>    	char abortstr[2];
>>>>    
>>>> -	if (abort)
>>>> -		strcpy(abortstr, "F");
>>>> -	else
>>>> -		strcpy(abortstr, "T");
>>>
>>> While at least in principle a compiler might be able to transform this into
>>> code not using any library function at all, ...
>>>
>>>> +	strscpy(abortstr, abort ? "F" : "T");
>>>
>>> ... the use of a n on-standard function (without equivalent compiler builtin)
>>> doesn't permit this. IOW why not simply switch to e.g.
>>>
>>>       char abortstr[2] = { [0] = abort ? 'F' : 'T' };
>>
>> I would even go further and drop abortstr[] completely:
>>
>> diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c
>> index 528682bf0c7f..c891af7165f5 100644
>> --- a/drivers/xen/xenbus/xenbus_xs.c
>> +++ b/drivers/xen/xenbus/xenbus_xs.c
>> @@ -550,14 +550,8 @@ EXPORT_SYMBOL_GPL(xenbus_transaction_start);
>>     */
>>    int xenbus_transaction_end(struct xenbus_transaction t, int abort)
>>    {
>> -       char abortstr[2];
>> -
>> -       if (abort)
>> -               strcpy(abortstr, "F");
>> -       else
>> -               strcpy(abortstr, "T");
>> -
>> -       return xs_error(xs_single(t, XS_TRANSACTION_END, abortstr, NULL));
>> +       return xs_error(xs_single(t, XS_TRANSACTION_END, abort ? "F" : "T",
>> +                       NULL));
>>    }
>>    EXPORT_SYMBOL_GPL(xenbus_transaction_end);
> 
> Hmm, which xs_single() indeed takes a const char *, it then casts away const-
> ness before handing to xs_talkv().

Yes, the cast is needed as xs_talkv() can handle reads and writes. No problem in
this case, as the string is only read by xs_talkv() (write type operation).


Juergen

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