[PATCH] drm/amd/display: fix a NULL pointer dereference in amdgpu_dm_i2c_xfer()

[Mario Limonciello]

When ddc_service_construct() is called, it explicitly checks both the
link type and whether there is something on the link which will
dictate whether the pin is marked as hw_supported.

If the ping isn't set or the link is not set (such as from
unloading/reloading amdgpu in an IGT test) then fail the
amdgpu_dm_i2c_xfer() call.

Cc: stable at vger.kernel.org
Fixes: 22676bc500c2 ("drm/amd/display: Fix dmub soft hang for PSR 1")
Link: https://github.com/fwupd/fwupd/issues/6327
Signed-off-by: Mario Limonciello <mario.limonciello at amd.com>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index adbeb2c897b5..e3b08b3a3c5f 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -7465,7 +7465,8 @@ static int amdgpu_dm_i2c_xfer(struct i2c_adapter *i2c_adap,
 
 	cmd.payloads = kcalloc(num, sizeof(struct i2c_payload), GFP_KERNEL);
 
-	if (!cmd.payloads)
+	if (!cmd.payloads || !ddc_service->ddc_pin ||
+	    !ddc_service->ddc_pin->hw_info.hw_supported)
 		return result;
 
 	cmd.number_of_payloads = num;
-- 
2.34.1