RE: [PATCH][next] drm/amdgpu/powerplay: fix dereference before null check of pointer hwmgr

[Quan, Evan]

Reviewed-by: Evan Quan <evan.quan@xxxxxxx>

-----Original Message-----
From: Colin King <colin.king@xxxxxxxxxxxxx> 
Sent: Friday, November 15, 2019 5:48 PM
To: Rex Zhu <rex.zhu@xxxxxxx>; Quan, Evan <Evan.Quan@xxxxxxx>; Deucher, Alexander <Alexander.Deucher@xxxxxxx>; Koenig, Christian <Christian.Koenig@xxxxxxx>; Zhou, David(ChunMing) <David1.Zhou@xxxxxxx>; David Airlie <airlied@xxxxxxxx>; Daniel Vetter <daniel@xxxxxxxx>; amd-gfx@xxxxxxxxxxxxxxxxxxxxx; dri-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: kernel-janitors@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
Subject: [PATCH][next] drm/amdgpu/powerplay: fix dereference before null check of pointer hwmgr

From: Colin Ian King <colin.king@xxxxxxxxxxxxx>

The assignment of adev dereferences pointer hwmgr before hwmgr is null checked, hence there is a potential null pointer deference issue. Fix this by assigning adev after the null check.

Addresses-Coverity: ("Dereference before null check")
Fixes: 0896d2f7ba4d ("drm/amdgpu/powerplay: properly set PP_GFXOFF_MASK")
Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
---
 drivers/gpu/drm/amd/powerplay/hwmgr/hwmgr.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/powerplay/hwmgr/hwmgr.c b/drivers/gpu/drm/amd/powerplay/hwmgr/hwmgr.c
index 443625c83ec9..d2909c91d65b 100644
--- a/drivers/gpu/drm/amd/powerplay/hwmgr/hwmgr.c
+++ b/drivers/gpu/drm/amd/powerplay/hwmgr/hwmgr.c
@@ -81,7 +81,7 @@ static void hwmgr_init_workload_prority(struct pp_hwmgr *hwmgr)
 
 int hwmgr_early_init(struct pp_hwmgr *hwmgr)  {
-	struct amdgpu_device *adev = hwmgr->adev;
+	struct amdgpu_device *adev;
 
 	if (!hwmgr)
 		return -EINVAL;
@@ -96,6 +96,8 @@ int hwmgr_early_init(struct pp_hwmgr *hwmgr)
 	hwmgr_init_workload_prority(hwmgr);
 	hwmgr->gfxoff_state_changed_by_workload = false;
 
+	adev = hwmgr->adev;
+
 	switch (hwmgr->chip_family) {
 	case AMDGPU_FAMILY_CI:
 		adev->pm.pp_feature &= ~PP_GFXOFF_MASK;
--
2.20.1