svn commit: r264422 - head/sys/kern

[Konstantin Belousov]

On Sun, Apr 13, 2014 at 11:55:54PM +0200, Christian Brueffer wrote:
> On 4/13/14 11:46 PM, Konstantin Belousov wrote:
> > On Sun, Apr 13, 2014 at 09:23:16PM +0000, Christian Brueffer wrote:
> >> Author: brueffer
> >> Date: Sun Apr 13 21:23:15 2014
> >> New Revision: 264422
> >> URL: http://svnweb.freebsd.org/changeset/base/264422
> >>
> >> Log:
> >>   Free buf after usage.
> >>   
> >>   CID:		1199377
> >>   Found with:	Coverity Prevent(tm)
> >>   MFC after:	1 week
> >>
> >> Modified:
> >>   head/sys/kern/imgact_elf.c
> >>
> >> Modified: head/sys/kern/imgact_elf.c
> >> ==============================================================================
> >> --- head/sys/kern/imgact_elf.c	Sun Apr 13 21:13:33 2014	(r264421)
> >> +++ head/sys/kern/imgact_elf.c	Sun Apr 13 21:23:15 2014	(r264422)
> >> @@ -1746,8 +1746,10 @@ __elfN(note_threadmd)(void *arg, struct 
> >>  	size = 0;
> >>  	__elfN(dump_thread)(td, buf, &size);
> >>  	KASSERT(*sizep == size, ("invalid size"));
> >> -	if (size != 0 && sb != NULL)
> >> +	if (size != 0 && sb != NULL) {
> >>  		sbuf_bcat(sb, buf, size);
> >> +		free(buf, M_TEMP);
> >> +	}
> >>  	*sizep = size;
> >>  }
> >>  
> > Why conditioning free() on size != 0 ?
> > IMO free(buf) must be done always, since buf is initialized for the case
> > when malloc() is not called.
> > 
> 
> The corresponding malloc() call is behind a similar conditional, so it
> seemed good to be symmetrical here (since buf if NULL otherwise anyway).
> 
> I can change it to call free() unconditionally if you prefer, I don't
> mind either way.

Yes, I think that unconditional call would be better, due to strange
interface of dump_thread.  It could modify the size, but for now this
is effectively disallowed by KASSERT().

Also, while there, I would change the code
	buf = NULL;
	if (size != 0 && sb != NULL)
		buf = malloc(size, M_TEMP, M_ZERO | M_WAITOK);
to avoid useless initialization if buf, like this:
	if (size != 0 && sb != NULL)
		buf = malloc(size, M_TEMP, M_ZERO | M_WAITOK);
	else
		buf = NULL;

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