linux-kernel - Re: [HPDD-discuss] [PATCH] staging: lustre: lustre: include: lustre_update.h: Fix for possible null pointer dereference

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Date:	Fri, 2 Jan 2015 17:55:50 +0000
From:	Ashley Pittman <apittman@....com>
To:	Rickard Strandqvist <rickard_strandqvist@...ctrumdigital.se>
CC:	Oleg Drokin <oleg.drokin@...el.com>,
	Andreas Dilger <andreas.dilger@...el.com>,
	"HPDD-discuss@...ts.01.org" <HPDD-discuss@...ts.01.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [HPDD-discuss] [PATCH] staging: lustre: lustre: include:
	lustre_update.h: Fix for possible null pointer dereference

Rickard,

> On 21 Dec 2014, at 22:43, Rickard Strandqvist <rickard_strandqvist@...ctrumdigital.se> wrote:
> 
> The NULL check was done to late, and there it was a risk
> of a possible null pointer dereference.
> 
> This was partially found by using a static code analysis program called cppcheck.
> 
> Signed-off-by: Rickard Strandqvist <rickard_strandqvist@...ctrumdigital.se>
> ---
> drivers/staging/lustre/lustre/include/lustre_update.h |    4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/lustre/lustre/include/lustre_update.h b/drivers/staging/lustre/lustre/include/lustre_update.h
> index 84defce..00e1361 100644
> --- a/drivers/staging/lustre/lustre/include/lustre_update.h
> +++ b/drivers/staging/lustre/lustre/include/lustre_update.h
> @@ -165,12 +165,14 @@ static inline int update_get_reply_buf(struct update_reply *reply, void **buf,
> 	int  result;
> 
> 	ptr = update_get_buf_internal(reply, index, &size);
> +
> +	LASSERT((ptr != NULL && size >= sizeof(int)));
> +
> 	result = *(int *)ptr;
> 
> 	if (result < 0)
> 		return result;
> 
> -	LASSERT((ptr != NULL && size >= sizeof(int)));

This looks odd to me, LASSERT is essentially BUG_ON() so is used for checking logic bugs.  Moving LASSERT calls doesn’t seem the correct way of resolving a logic problem and if you’re doing static analysis it might be more productive to do it this with LASSERT disabled.

> 	*buf = ptr + sizeof(int);
> 	return size - sizeof(int);
> }
> -- 
> 1.7.10.4
> 
> _______________________________________________
> HPDD-discuss mailing list
> HPDD-discuss@...ts.01.org
> https://lists.01.org/mailman/listinfo/hpdd-discuss

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