[PATCH 5.9 240/757] video: fbdev: sis: fix null ptr dereference

Greg Kroah-Hartman
2020-10-27T15:41:39Z

From: Tom Rix <trix@redhat.com>

[ Upstream commit ad6f93e9cd56f0b10e9b22e3e137d17a1a035242 ]

Clang static analysis reports this representative error

init.c:2501:18: warning: Array access (from variable 'queuedata') results
in a null pointer dereference
templ |= ((queuedata[i] & 0xc0) << 3);

This is the problem block of code

if(ModeNo > 0x13) {
...
if(SiS_Pr->ChipType == SIS_730) {
queuedata = &FQBQData730[0];
} else {
queuedata = &FQBQData[0];
}
} else {

}

queuedata is not set in the else block

Reviewing the old code, the arrays FQBQData730 and FQBQData were
used directly.

So hoist the setting of queuedata out of the if-else block.

Fixes: 544393fe584d ("[PATCH] sisfb update")
Signed-off-by: Tom Rix <trix@redhat.com>
Cc: Thomas Winischhofer <thomas@winischhofer.net>
Cc: Andrew Morton <akpm@osdl.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200805145208.17727-1-trix@redhat.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/video/fbdev/sis/init.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/video/fbdev/sis/init.c b/drivers/video/fbdev/sis/init.c
index dfe3eb769638b..fde27feae5d0c 100644
--- a/drivers/video/fbdev/sis/init.c
+++ b/drivers/video/fbdev/sis/init.c
@@ -2428,6 +2428,11 @@ SiS_SetCRT1FIFO_630(struct SiS_Private *SiS_Pr, unsigned short ModeNo,

i = 0;

+ if (SiS_Pr->ChipType == SIS_730)
+ queuedata = &FQBQData730[0];
+ else
+ queuedata = &FQBQData[0];
+
if(ModeNo > 0x13) {

/* Get VCLK */
@@ -2445,12 +2450,6 @@ SiS_SetCRT1FIFO_630(struct SiS_Private *SiS_Pr, unsigned short ModeNo,
/* Get half colordepth */
colorth = colortharray[(SiS_Pr->SiS_ModeType - ModeEGA)];

- if(SiS_Pr->ChipType == SIS_730) {
- queuedata = &FQBQData730[0];
- } else {
- queuedata = &FQBQData[0];
- }
-
do {
templ = SiS_CalcDelay2(SiS_Pr, queuedata[i]) * VCLK * colorth;

--
2.25.1