linux-kernel - Re: [PATCH] staging: lustre: lustre: obdclass: lprocfs_status.c: Fix for possible null pointer dereference

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Date:	Sun, 14 Dec 2014 17:51:37 -0800
From:	Joe Perches <joe@...ches.com>
To:	Rickard Strandqvist <rickard_strandqvist@...ctrumdigital.se>
Cc:	Oleg Drokin <oleg.drokin@...el.com>,
	Andreas Dilger <andreas.dilger@...el.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Julia Lawall <Julia.Lawall@...6.fr>,
	Greg Donald <gdonald@...il.com>,
	"John L. Hammond" <john.hammond@...el.com>,
	Andriy Skulysh <Andriy_Skulysh@...atex.com>,
	Fabian Frederick <fabf@...net.be>,
	James Simmons <uja.ornl@...il.com>, HPDD-discuss@...ts.01.org,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: lustre: lustre: obdclass: lprocfs_status.c: 
 Fix for possible null pointer dereference

On Sun, 2014-12-14 at 23:52 +0100, Rickard Strandqvist wrote:
> There is otherwise a risk of a possible null pointer dereference.
> 
> Was largely found by using a static code analysis program called cppcheck.

Perhaps the tool could use a little work.
It's not possible for end to be NULL no?

unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int base)
{
	unsigned long long result;
	unsigned int rv;

	cp = _parse_integer_fixup_radix(cp, &base);
	rv = _parse_integer(cp, base, &result);
	/* FIXME */
	cp += (rv & ~KSTRTOX_OVERFLOW);

	if (endp)
		*endp = (char *)cp;

	return result;
}
EXPORT_SYMBOL(simple_strtoull);


> diff --git a/drivers/staging/lustre/lustre/obdclass/lprocfs_status.c b/drivers/staging/lustre/lustre/obdclass/lprocfs_status.c
[]

Above this:

	whole = simple_strtoull(pbuf, &end, 10);

> +++ b/drivers/staging/lustre/lustre/obdclass/lprocfs_status.c
> @@ -1897,17 +1897,19 @@ int lprocfs_write_frac_u64_helper(const char *buffer, unsigned long count,
>  	}
>  
>  	units = 1;
> -	switch (*end) {
> -	case 'p': case 'P':
> -		units <<= 10;
> -	case 't': case 'T':
> -		units <<= 10;
> -	case 'g': case 'G':
> -		units <<= 10;
> -	case 'm': case 'M':
> -		units <<= 10;
> -	case 'k': case 'K':
> -		units <<= 10;
> +	if (end) {
> +		switch (*end) {
> +		case 'p': case 'P':
> +			units <<= 10;
> +		case 't': case 'T':
> +			units <<= 10;
> +		case 'g': case 'G':
> +			units <<= 10;
> +		case 'm': case 'M':
> +			units <<= 10;
> +		case 'k': case 'K':
> +			units <<= 10;
> +		}

The only thing I might do is

	switch (tolower(*end)) {

and remove the second case entry for each line

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