drm/amd/amdgpu: Fix missing null check in atombios_i2c.c

Reported by smatch:
amdgpu_atombios_i2c_process_i2c_ch() error: we previously assumed 'buf' could be null

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Ernst Sjöstrand <ernstp@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

1 files changed, 9 insertions, 2 deletions

diff --git a/drivers/gpu/drm/amd/amdgpu/atombios_i2c.c b/drivers/gpu/drm/amd/amdgpu/atombios_i2c.c
index b374653bd6cf..f9b2ce9a98f3 100644
--- a/drivers/gpu/drm/amd/amdgpu/atombios_i2c.c
+++ b/drivers/gpu/drm/amd/amdgpu/atombios_i2c.c
@@ -65,8 +65,15 @@ static int amdgpu_atombios_i2c_process_i2c_ch(struct amdgpu_i2c_chan *chan,
                         args.ucRegIndex = buf[0];
                 if (num)
                         num--;
-                if (num)
-                        memcpy(&out, &buf[1], num);
+                if (num) {
+                        if (buf) {
+                                memcpy(&out, &buf[1], num);
+                        } else {
+                                DRM_ERROR("hw i2c: missing buf with num > 1\n");
+                                r = -EINVAL;
+                                goto done;
+                        }
+                }
                 args.lpI2CDataOut = cpu_to_le16(out);
         } else {
                 if (num > ATOM_MAX_HW_I2C_READ) {