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

[Wenlin Kang]

On 5/12/19 5:00 PM, Daniel Thompson wrote:
> On Thu, May 09, 2019 at 10:56:03AM +0800, Wenlin Kang wrote:
> > 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.
> Sorry, I'm confused by this. What behavior does strscpy() have that you
> consider undesirable in this case?


Hi Daniel

I checked strscpy() again, and think either is fine to me, if you think 
strscpy() is better, I can change it to this, and send v2, thanks for 
your review.


> Daniel.

--
Thanks,
Wenlin Kang