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

[Neil Horman <nhorman@tuxdriver.com>]

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@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);