accel/amdxdna: Validate command buffer payload count

The count field in the command header is used to determine the valid
payload size. Verify that the valid payload does not exceed the remaining
buffer space.

Fixes: aac2430 ("accel/amdxdna: Add command execution")
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Signed-off-by: Lizhi Hou <lizhi.hou@amd.com>
Link: https://patch.msgid.link/20260219211946.1920485-1-lizhi.hou@amd.com

Author: houlz0507

drivers/accel/amdxdna/amdxdna_ctx.c

@@ -104,7 +104,10 @@ void *amdxdna_cmd_get_payload(struct amdxdna_gem_obj *abo, u32 *size)
 
 	if (size) {
 		count = FIELD_GET(AMDXDNA_CMD_COUNT, cmd->header);
-		if (unlikely(count <= num_masks)) {
+		if (unlikely(count <= num_masks ||
+			     count * sizeof(u32) +
+			     offsetof(struct amdxdna_cmd, data[0]) >
+			     abo->mem.size)) {
 			*size = 0;
 			return NULL;
 		}