[PATCH v2 1/1] drm/mediatek: Fix potential KP on 0 bytes nvmem cell read

[Liankun Yang <liankun.yang@mediatek.com>]

If the len is 0, kernel crash will occur when performing operations.
Add the len check conditions to prevent kernel crash.

Fixes: f70ac097a2cf ("drm/mediatek: Add MT8195 Embedded DisplayPort driver")
Signed-off-by: Liankun Yang <liankun.yang@mediatek.com>
---
Changes in V2:
- Fix the commit title.
- Remove blank line between the Fixes and Signe-off-by.
- Modify the judgment writing method.
Per suggestion from the previous thread:
https://patchwork.kernel.org/project/linux-mediatek/patch/20240925084116.28848-1-liankun.yang@mediatek.com/
---
 drivers/gpu/drm/mediatek/mtk_dp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
index d8796a904eca..9ecdf62398ee 100644
--- a/drivers/gpu/drm/mediatek/mtk_dp.c
+++ b/drivers/gpu/drm/mediatek/mtk_dp.c
@@ -1082,7 +1082,7 @@ static void mtk_dp_get_calibration_data(struct mtk_dp *mtk_dp)
 	buf = (u32 *)nvmem_cell_read(cell, &len);
 	nvmem_cell_put(cell);
 
-	if (IS_ERR(buf) || ((len / sizeof(u32)) != 4)) {
+	if (IS_ERR(buf) || !len || ((len / sizeof(u32)) != 4)) {
 		dev_warn(dev, "Failed to read nvmem_cell_read\n");
 
 		if (!IS_ERR(buf))
-- 
2.45.2