linux-kernel - [PATCH V2] drm/xe/guc: Fix dereference before Null check

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Message-ID: <20241009213922.37962-1-everestkc@everestkc.com.np>
Date: Wed,  9 Oct 2024 15:39:20 -0600
From: "Everest K.C." <everestkc@...restkc.com.np>
To: lucas.demarchi@...el.com,
	thomas.hellstrom@...ux.intel.com,
	rodrigo.vivi@...el.com,
	maarten.lankhorst@...ux.intel.com,
	mripard@...nel.org,
	tzimmermann@...e.de,
	airlied@...il.com,
	simona@...ll.ch
Cc: "Everest K.C." <everestkc@...restkc.com.np>,
	skhan@...uxfoundation.org,
	dan.carpenter@...aro.org,
	intel-xe@...ts.freedesktop.org,
	dri-devel@...ts.freedesktop.org,
	kernel-janitors@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH V2] drm/xe/guc: Fix dereference before Null check

The pointer list->list is derefrenced before the Null check.
Fix this by moving the Null check outside the for loop, so that
the check is performed before the derefrencing.

This issue was reported by Coverity Scan.
https://scan7.scan.coverity.com/#/project-view/51525/11354
?selectedIssue=1600335

Fixes: a18c696fa5cb ("drm/xe/guc: Fix dereference before Null check")

Signed-off-by: Everest K.C. <everestkc@...restkc.com.np>
---
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