diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index feba32f43472..362ef7810fdb 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -784,11 +784,13 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client,
 	}
 
 	if (verbose) {
-		acs_list.buffer[acs_list.len-1] = 0; /* drop final semicolon */
+		/* Drop the final semicolon; the list is not empty here */
+		if (!seq_buf_has_overflowed(&acs_list))
+			acs_list.buffer[acs_list.len - 1] = '\0';
 		pci_warn(client, "ACS redirect is set between the client and provider (%s)\n",
 			 pci_name(provider));
 		pci_warn(client, "to disable ACS redirect for this path, add the kernel parameter: pci=disable_acs_redir=%s\n",
-			 acs_list.buffer);
+			 seq_buf_str(&acs_list));
 	}
 	acs_redirects = true;