linux-kernel - Re: [PATCH] crypto: qat - use strscpy_pad to simplify buffer initialization

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Message-Id: <6DB96B06-108C-465B-9A54-88B8008DDD60@linux.dev>
Date: Thu, 23 Oct 2025 17:35:00 +0200
From: Thorsten Blum <thorsten.blum@...ux.dev>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Giovanni Cabiddu <giovanni.cabiddu@...el.com>,
 Herbert Xu <herbert@...dor.apana.org.au>,
 "David S. Miller" <davem@...emloft.net>,
 Jack Xu <jack.xu@...el.com>,
 Suman Kumar Chakraborty <suman.kumar.chakraborty@...el.com>,
 Qianfeng Rong <rongqianfeng@...o.com>,
 qat-linux@...el.com,
 linux-crypto@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] crypto: qat - use strscpy_pad to simplify buffer
 initialization

On 22. Oct 2025, at 20:17, Andy Shevchenko wrote:
> On Wed, Oct 22, 2025 at 02:36:19PM +0200, Thorsten Blum wrote:
>> Use strscpy_pad() to copy the string and zero-pad the destination buffer
>> in a single step instead of zero-initializing the buffer first and then
>> immediately overwriting it using strscpy().
>> 
>> Replace the magic number 16 with sizeof(buf) and remove the redundant
>> parentheses around kstrtoul() while we're at it.
> 
> I understand that you focused on strscpy*() conversions, but the below I think
> needs a bigger refactoring, see my remarks.
> 
> ...
> 
>> -	char buf[16] = {0};
>> +	char buf[16] = {};

Sorry, this should have been just 'char buf[16];' since {} and {0} are
equivalent and both zero-initialize the array.

>> 	unsigned long ae = 0;
>> 	int i;
>> 
>> -	strscpy(buf, str, sizeof(buf));
>> -	for (i = 0; i < 16; i++) {
>> +	strscpy_pad(buf, str);
> 
> First of all, why do we need a _pad() version here? Is the data somehow being
> used as a whole?

I honestly didn't question this, but it looks like strscpy() would be
sufficient (with this approach at least).

>> +	for (i = 0; i < sizeof(buf); i++) {
>> 		if (!isdigit(buf[i])) {
>> 			buf[i] = '\0';
>> 			break;
>> 		}
>> 	}
>> -	if ((kstrtoul(buf, 10, &ae)))
>> +	if (kstrtoul(buf, 10, &ae))
>> 		return -EFAULT;
> 
> Looking at this, it tries to work around the kstrtoul() inability to perform
> partial parses. Instead, this should do something like
> 
> 	unsigned long long x;
> 	const char *end;
> 
> 	simple_strtoull(...);
> 	if (x > UINT_MAX || end == buf)
> 		return $ERR; // wrong input / overflow

How about this?

diff --git a/drivers/crypto/intel/qat/qat_common/qat_uclo.c b/drivers/crypto/intel/qat/qat_common/qat_uclo.c
index 18c3e4416dc5..04628dc01456 100644
--- a/drivers/crypto/intel/qat/qat_common/qat_uclo.c
+++ b/drivers/crypto/intel/qat/qat_common/qat_uclo.c
@@ -200,20 +200,12 @@ qat_uclo_cleanup_batch_init_list(struct icp_qat_fw_loader_handle *handle,
 
 static int qat_uclo_parse_num(char *str, unsigned int *num)
 {
-	char buf[16] = {0};
-	unsigned long ae = 0;
-	int i;
-
-	strscpy(buf, str, sizeof(buf));
-	for (i = 0; i < 16; i++) {
-		if (!isdigit(buf[i])) {
-			buf[i] = '\0';
-			break;
-		}
-	}
-	if ((kstrtoul(buf, 10, &ae)))
-		return -EFAULT;
+	unsigned long long ae;
+	char *end;
 
+	ae = simple_strtoull(str, &end, 10);
+	if (ae > UINT_MAX || str == end || (end - str) > 20)
+		return -EINVAL;
 	*num = (unsigned int)ae;
 	return 0;
 }