linux-kernel - Re: [PATCH V4] drm/xe/guc: Fix dereference before NULL check

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Message-ID: <ZxlYbVOLPQv-oWrv@intel.com>
Date: Wed, 23 Oct 2024 16:11:25 -0400
From: Rodrigo Vivi <rodrigo.vivi@...el.com>
To: Everest K.C. <everestkc@...restkc.com.np>
CC: <lucas.demarchi@...el.com>, <thomas.hellstrom@...ux.intel.com>,
	<maarten.lankhorst@...ux.intel.com>, <mripard@...nel.org>,
	<tzimmermann@...e.de>, <airlied@...il.com>, <simona@...ll.ch>,
	<skhan@...uxfoundation.org>, <dan.carpenter@...aro.org>,
	<michal.wajdeczko@...el.com>, <intel-xe@...ts.freedesktop.org>,
	<dri-devel@...ts.freedesktop.org>, <kernel-janitors@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V4] drm/xe/guc: Fix dereference before NULL check

On Thu, Oct 10, 2024 at 10:57:59AM -0600, Everest K.C. wrote:
> The pointer list->list is dereferenced before the NULL check.
> Fix this by moving the NULL check outside the for loop, so that
> the check is performed before the dereferencing.
> The list->list pointer cannot be NULL so this has no effect on runtime.
> It's just a correctness issue.
> 
> This issue was reported by Coverity Scan.
> https://scan7.scan.coverity.com/#/project-view/51525/11354?selectedIssue=1600335
> 
> Fixes: 0f1fdf559225 ("drm/xe/guc: Save manual engine capture into capture list")
> Signed-off-by: Everest K.C. <everestkc@...restkc.com.np>
> Reviewed-by: Dan Carpenter <dan.carpenter@...aro.org>
> ---
> V3 -> V4: - Corrected the Fixes tag
>           - Added Reviewed-by tag

For some reason it looks like nor CI nor lore has this v4 version.

could you please resubmit it?

> V2 -> V3: - Changed Null to NULL in the changelog
>           - Corrected typo in the changelong
>           - Added more description to the changelong
> 	  - Fixed the link for Coverity Report
> 	  - Removed the space after the Fixes tag
> V1 -> V2: - Combined the `!list->list` check in preexisting if statement
> 	  - Added Fixes tag 
> 	  - Added the link to the Coverity Scan report 
> 
>  drivers/gpu/drm/xe/xe_guc_capture.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_guc_capture.c b/drivers/gpu/drm/xe/xe_guc_capture.c
> index 41262bda20ed..947c3a6d0e5a 100644
> --- a/drivers/gpu/drm/xe/xe_guc_capture.c
> +++ b/drivers/gpu/drm/xe/xe_guc_capture.c
> @@ -1531,7 +1531,7 @@ read_reg_to_node(struct xe_hw_engine *hwe, const struct __guc_mmio_reg_descr_gro
>  {
>  	int i;
>  
> -	if (!list || list->num_regs == 0)
> +	if (!list || !list->list || list->num_regs == 0)
>  		return;
>  
>  	if (!regs)
> @@ -1541,9 +1541,6 @@ read_reg_to_node(struct xe_hw_engine *hwe, const struct __guc_mmio_reg_descr_gro
>  		struct __guc_mmio_reg_descr desc = list->list[i];
>  		u32 value;
>  
> -		if (!list->list)
> -			return;
> -
>  		if (list->type == GUC_STATE_CAPTURE_TYPE_ENGINE_INSTANCE) {
>  			value = xe_hw_engine_mmio_read32(hwe, desc.reg);
>  		} else {
> -- 
> 2.43.0
>