[PATCH] drm/amdxcp: Add more checks to amdxcp

[Lijo Lazar]

Add NULL check to ddev argument and guard pdev_num against underflow.

Signed-off-by: Lijo Lazar <lijo.la...@amd.com>
---
 drivers/gpu/drm/amd/amdxcp/amdgpu_xcp_drv.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdxcp/amdgpu_xcp_drv.c 
b/drivers/gpu/drm/amd/amdxcp/amdgpu_xcp_drv.c
index ae40f64369ab..a569163de047 100644
--- a/drivers/gpu/drm/amd/amdxcp/amdgpu_xcp_drv.c
+++ b/drivers/gpu/drm/amd/amdxcp/amdgpu_xcp_drv.c
@@ -44,7 +44,7 @@ static const struct drm_driver amdgpu_xcp_driver = {
        .minor = 0,
 };
 
-static int8_t pdev_num;
+static u8 pdev_num;
 static struct xcp_device *xcp_dev[MAX_XCP_PLATFORM_DEVICE];
 static DEFINE_MUTEX(xcp_mutex);
 
@@ -56,6 +56,10 @@ int amdgpu_xcp_drm_dev_alloc(struct drm_device **ddev)
        int ret, i;
 
        static_assert(sizeof(dev_name) >= sizeof("amdgpu_xcp_") + 10);
+       if (!ddev)
+               return -EINVAL;
+
+       BUILD_BUG_ON(MAX_XCP_PLATFORM_DEVICE >= U8_MAX);
 
        guard(mutex)(&xcp_mutex);
 
@@ -102,7 +106,7 @@ int amdgpu_xcp_drm_dev_alloc(struct drm_device **ddev)
 }
 EXPORT_SYMBOL(amdgpu_xcp_drm_dev_alloc);
 
-static void free_xcp_dev(int8_t index)
+static void free_xcp_dev(uint8_t index)
 {
        if ((index < MAX_XCP_PLATFORM_DEVICE) && (xcp_dev[index])) {
                struct platform_device *pdev = xcp_dev[index]->pdev;
@@ -111,17 +115,18 @@ static void free_xcp_dev(int8_t index)
                platform_device_unregister(pdev);
 
                xcp_dev[index] = NULL;
-               pdev_num--;
+               if (pdev_num > 0)
+                       pdev_num--;
        }
 }
 
 void amdgpu_xcp_drm_dev_free(struct drm_device *ddev)
 {
-       int8_t i;
+       uint8_t i;
 
        guard(mutex)(&xcp_mutex);
 
-       for (i = 0; i < MAX_XCP_PLATFORM_DEVICE; i++) {
+       for (i = 0; pdev_num && i < MAX_XCP_PLATFORM_DEVICE; i++) {
                if ((xcp_dev[i]) && (&xcp_dev[i]->drm == ddev)) {
                        free_xcp_dev(i);
                        break;
@@ -132,7 +137,7 @@ EXPORT_SYMBOL(amdgpu_xcp_drm_dev_free);
 
 void amdgpu_xcp_drv_release(void)
 {
-       int8_t i;
+       uint8_t i;
 
        guard(mutex)(&xcp_mutex);
 
-- 
2.49.0