Re: [PATCH] kdb: Fix bound check compiler warning

[Wenlin Kang]

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@xxxxxxxxxxxxx>
> > ---
> >   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