habanalabs/gaudi: fix comment to reflect current code

Due to code changes in the past few years, the original comment of
how parser->user_cb_size is checked was not correct anymore.

Fix it to reflect current code and add more explanation as the code
is more complex now.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>

diff --git a/drivers/misc/habanalabs/gaudi/gaudi.c b/drivers/misc/habanalabs/gaudi/gaudi.c
index c16c0f9fe20269f5fdd03aed83c696708bf85676..72b0d145e8530d7c80f1054f73a638ea51cb8eb4 100644 (file)
--- a/drivers/misc/habanalabs/gaudi/gaudi.c
+++ b/drivers/misc/habanalabs/gaudi/gaudi.c
@@ -5562,8 +5562,14 @@ static int gaudi_parse_cb_mmu(struct hl_device *hdev,
        }
 
        /*
-        * The check that parser->user_cb_size <= parser->user_cb->size was done
-        * in validate_queue_index().
+        * We are protected from overflow because the check
+        * "parser->user_cb_size <= parser->user_cb->size" was done in get_cb_from_cs_chunk()
+        * in the common code. That check is done only if is_kernel_allocated_cb is true.
+        *
+        * There is no option to reach here without going through that check because:
+        * 1. validate_queue_index() assigns true to is_kernel_allocated_cb for any submission to
+        *    an external queue.
+        * 2. For Gaudi, we only parse CBs that were submitted to the external queues.
         */
        memcpy(parser->patched_cb->kernel_address,
                parser->user_cb->kernel_address,