[PATCH 5.18 358/879] drm/v3d: Fix null pointer dereference of pointer perfmon

Greg Kroah-Hartman
2022-06-07T22:42:38Z

From: Colin Ian King <colin.i.king@gmail.com>

[ Upstream commit ce7a1ecf3f9f1fccaf67295307614511d8e11b13 ]

In the unlikely event that pointer perfmon is null the WARN_ON return path
occurs after the pointer has already been deferenced. Fix this by only
dereferencing perfmon after it has been null checked.

Fixes: 26a4dc29b74a ("drm/v3d: Expose performance counters to userspace")
Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Reviewed-by: Juan A. Suarez <jasuarez@igalia.com>
Signed-off-by: Melissa Wen <melissa.srw@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220424183512.1365683-1-colin.i.king@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/v3d/v3d_perfmon.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/v3d/v3d_perfmon.c b/drivers/gpu/drm/v3d/v3d_perfmon.c
index 0288ef063513..f6a88abccc7d 100644
--- a/drivers/gpu/drm/v3d/v3d_perfmon.c
+++ b/drivers/gpu/drm/v3d/v3d_perfmon.c
@@ -25,11 +25,12 @@ void v3d_perfmon_start(struct v3d_dev *v3d, struct v3d_perfmon *perfmon)
{
unsigned int i;
u32 mask;
- u8 ncounters = perfmon->ncounters;
+ u8 ncounters;

if (WARN_ON_ONCE(!perfmon || v3d->active_perfmon))
return;

+ ncounters = perfmon->ncounters;
mask = GENMASK(ncounters - 1, 0);

for (i = 0; i < ncounters; i++) {
--
2.35.1