drm/msm/sde: sanitize debugfs inputs when reading mdp memory

Sanitize debugfs inputs to only allow access to mdp memory block
specified in dtsi file. This change will allow only one single block
to be read at the time and will avoid accessing memory outside of valid
decode space which can trigger AHB error bus response.

Change-Id: I91b91ac2b31eac4facb0c402c92ed8fcfc01d91e
Signed-off-by: Amine Najahi <anajahi@codeaurora.org>

drivers/gpu/drm/msm/sde_dbg.c

@@ -1897,6 +1897,37 @@ static int sde_dbg_reg_base_release(struct inode *inode, struct file *file)
 	return 0;
 }
 
+/**
+ * sde_dbg_reg_base_is_valid_range - verify if requested memory range is valid
+ * @off: address offset in bytes
+ * @cnt: memory size in bytes
+ * Return: true if valid; false otherwise
+ */
+static bool sde_dbg_reg_base_is_valid_range(u32 off, u32 cnt)
+{
+	static struct sde_dbg_base *dbg_base = &sde_dbg_base;
+	struct sde_dbg_reg_range *node;
+	struct sde_dbg_reg_base *base;
+
+	pr_debug("check offset=0x%x cnt=0x%x\n", off, cnt);
+
+	list_for_each_entry(base, &dbg_base->reg_base_list, reg_base_head) {
+		list_for_each_entry(node, &base->sub_range_list, head) {
+			pr_debug("%s: start=0x%x end=0x%x\n", node->range_name,
+					node->offset.start, node->offset.end);
+
+			if (node->offset.start <= off
+					&& off <= node->offset.end
+					&& off + cnt <= node->offset.end) {
+				pr_debug("valid range requested\n");
+				return true;
+			}
+		}
+	}
+
+	pr_err("invalid range requested\n");
+	return false;
+}
 
 /**
  * sde_dbg_reg_base_offset_write - set new offset and len to debugfs reg base
@@ -1951,8 +1982,15 @@ static ssize_t sde_dbg_reg_base_offset_write(struct file *file,
 		goto exit;
 	}
 
-	if (cnt == 0)
-		return -EINVAL;
+	if (cnt == 0) {
+		rc = -EINVAL;
+		goto exit;
+	}
+
+	if (!sde_dbg_reg_base_is_valid_range(off, cnt)) {
+		rc = -EINVAL;
+		goto exit;
+	}
 
 	dbg->off = off;
 	dbg->cnt = cnt;