linux-kernel - [PATCH 5.15 078/177] drm/ast: potential dereference of null pointer

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Message-Id: <20211220143042.731219145@linuxfoundation.org>
Date:   Mon, 20 Dec 2021 15:33:48 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jiasheng Jiang <jiasheng@...as.ac.cn>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 078/177] drm/ast: potential dereference of null pointer

From: Jiasheng Jiang <jiasheng@...as.ac.cn>

[ Upstream commit fea3fdf975dd9f3e5248afaab8fe023db313f005 ]

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>
Signed-off-by: Thomas Zimmermann <tzimmermann@...e.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20211214014126.2211535-1-jiasheng@iscas.ac.cn
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 1e30eaeb0e1b3..d5c98f79d58d3 100644
--- a/drivers/gpu/drm/ast/ast_mode.c
+++ b/drivers/gpu/drm/ast/ast_mode.c
@@ -1121,7 +1121,10 @@ 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 *
-- 
2.33.0