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

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Message-ID: <13cbd826-540e-4352-8e0d-ae0c9fbd2faa@suse.com>
Date: Mon, 13 Oct 2025 10:22:57 +0200
From: Jan Beulich <jbeulich@...e.com>
To: Jürgen Groß <jgross@...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 13.10.2025 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().

Jan