linux-kernel - Re: [PATCH] kdb: Fix bound check compiler warning

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Date:   Thu, 9 May 2019 10:56:03 +0800
From:   Wenlin Kang <wenlin.kang@...driver.com>
To:     Daniel Thompson <daniel.thompson@...aro.org>
CC:     <jason.wessel@...driver.com>, <prarit@...hat.com>,
        <kgdb-bugreport@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kdb: Fix bound check compiler warning

On 5/8/19 4:16 PM, Daniel Thompson wrote:
> On Wed, May 08, 2019 at 09:52:39AM +0800, Wenlin Kang wrote:
>> The strncpy() function may leave the destination string buffer
>> unterminated, better use strlcpy() instead.
>>
>> This fixes the following warning with gcc 8.2:
>>
>> kernel/debug/kdb/kdb_io.c: In function 'kdb_getstr':
>> kernel/debug/kdb/kdb_io.c:449:3: warning: 'strncpy' specified bound 256 equals destination size [-Wstringop-truncation]
>>     strncpy(kdb_prompt_str, prompt, CMD_BUFLEN);
>>     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>> Signed-off-by: Wenlin Kang <wenlin.kang@...driver.com>
>> ---
>>   kernel/debug/kdb/kdb_io.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c
>> index 6a4b414..7fd4513 100644
>> --- a/kernel/debug/kdb/kdb_io.c
>> +++ b/kernel/debug/kdb/kdb_io.c
>> @@ -446,7 +446,7 @@ static char *kdb_read(char *buffer, size_t bufsize)
>>   char *kdb_getstr(char *buffer, size_t bufsize, const char *prompt)
>>   {
>>   	if (prompt && kdb_prompt_str != prompt)
>> -		strncpy(kdb_prompt_str, prompt, CMD_BUFLEN);
>> +		strlcpy(kdb_prompt_str, prompt, CMD_BUFLEN);
> Shouldn't that be strscpy?


Hi Daniel

I thought about strscpy, but I think strlcpy is better, because it only 
copy the real number of characters if src string less than that size.


>
>
> Daniel.
>
>>   	kdb_printf(kdb_prompt_str);
>>   	kdb_nextline = 1;	/* Prompt and input resets line number */
>>   	return kdb_read(buffer, bufsize);
>> -- 
>> 1.9.1
>>

-- 
Thanks,
Wenlin Kang