[dpdk-dev] [PATCH] pmdinfogen: fix resource leak of FILE object

[Bruce Richardson]

On Fri, Feb 02, 2018 at 07:44:39AM -0500, Neil Horman wrote:
> On Fri, Feb 02, 2018 at 12:00:58PM +0000, Bruce Richardson wrote:
> > Coverity flags an issue where the resources used by the FILE object for
> > the temporary input file are leaked. This is a very minor issue, but is
> > easily fixed, while also avoiding later problems where we try to close
> > an invalid file descriptor in the failure case.
> > 
> > The fix is to use "dup()" to get a new file descriptor number rather than
> > using the value directly from fileno. This allows us to close the file
> > opened with tmpfile() within in scope block, while allowing the duplicate
> > to pass to the outer block and be closed when the function terminates.
> > 
> > As a side-effect I/O in the function is therefore changed from using stdio
> > fread/fwrite to read/write system calls.
> > 
> > Coverity issue: 260399
> > Fixes: 0d68533617e3 ("pmdinfogen: allow using stdin and stdout")
> > 
> > Signed-off-by: Bruce Richardson <bruce.richardson at intel.com>
> > ---
> >  buildtools/pmdinfogen/pmdinfogen.c | 16 ++++++++++------
> >  1 file changed, 10 insertions(+), 6 deletions(-)
> > 
> > diff --git a/buildtools/pmdinfogen/pmdinfogen.c b/buildtools/pmdinfogen/pmdinfogen.c
> > index 45b267346..0f35ca46b 100644
> > --- a/buildtools/pmdinfogen/pmdinfogen.c
> > +++ b/buildtools/pmdinfogen/pmdinfogen.c
> > @@ -50,20 +50,24 @@ static void *grab_file(const char *filename, unsigned long *size)
> >  		/* from stdin, use a temporary file to mmap */
> >  		FILE *infile;
> >  		char buffer[1024];
> > -		size_t n;
> > +		int n;
> >  
> >  		infile = tmpfile();
> >  		if (infile == NULL) {
> >  			perror("tmpfile");
> >  			return NULL;
> >  		}
> > -		while (!feof(stdin)) {
> > -			n = fread(buffer, 1, sizeof(buffer), stdin);
> > -			if (fwrite(buffer, 1, n, infile) != n)
> > +		fd = dup(fileno(infile));
> > +		fclose(infile);
> > +		if (fd < 0)
> > +			return NULL;
> > +
> > +		n = read(STDIN_FILENO, buffer, sizeof(buffer));
> > +		while (n > 0) {
> > +			if (write(fd, buffer, n) != n)
> >  				goto failed;
> > +			n = read(STDIN_FILENO, buffer, sizeof(buffer));
> >  		}
> > -		fflush(infile);
> > -		fd = fileno(infile);
> >  	}
> >  
> >  	if (fstat(fd, &st))
> > -- 
> > 2.14.3
> > 
> > 
> 
> Wouldn't it be just as good, and easier to check fd for == -1 as a condition of
> calling close?
> 
> like 
> failed:
> 	if (fd >= 0)
> 		close(fd);
> 
That would fix the problem of calling goto failed with fd set to -1, but
would not fix the resource issue that coverity was complaining about. We
were allocating a stdio FILE object, then taking just the fileno of it
and letting the file number go out of scope. This cleans this that up,
so that we just use file numbers and properly close the FILE * once it's
outlived its usefulness.

BTW: I did investigate using open and O_TMPFILE in place of tmpfile()
call, but while it would work great on Linux, it's not available
elsewhere, so tmpfile looks the best option.

Regards,
/Bruce