linux-kernel - [PATCH] drm/ast: potential dereference of null pointer

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Date:   Tue, 14 Dec 2021 09:37:27 +0800
From:   Jiasheng Jiang <jiasheng@...as.ac.cn>
To:     airlied@...hat.com, tzimmermann@...e.de, airlied@...ux.ie,
        daniel@...ll.ch
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Jiasheng Jiang <jiasheng@...as.ac.cn>
Subject: [PATCH] drm/ast: potential dereference of null pointer

The return value of kzalloc() needs to be checked.
To avoid use of null pointer '&ast_state->base' in case of the
failure of alloc.

Fixes: f0adbc382b8b ("drm/ast: Allocate initial CRTC state of the correct size")
Signed-off-by: Jiasheng Jiang <jiasheng@...as.ac.cn>
---
 drivers/gpu/drm/ast/ast_mode.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/ast/ast_mode.c b/drivers/gpu/drm/ast/ast_mode.c
index 36d9575aa27b..65099f0359f9 100644
--- a/drivers/gpu/drm/ast/ast_mode.c
+++ b/drivers/gpu/drm/ast/ast_mode.c
@@ -1120,7 +1120,10 @@ static void ast_crtc_reset(struct drm_crtc *crtc)
 	if (crtc->state)
 		crtc->funcs->atomic_destroy_state(crtc, crtc->state);
 
-	__drm_atomic_helper_crtc_reset(crtc, &ast_state->base);
+	if (ast_state)
+		__drm_atomic_helper_crtc_reset(crtc, &ast_state->base);
+	else
+		__drm_atomic_helper_crtc_reset(crtc, NULL);
 }
 
 static struct drm_crtc_state *
-- 
2.25.1