[PATCH] nvmet: fixup buffer overrun in nvmet_subsys_attr_serial()

[Christoph Hellwig]

On Fri, Aug 27, 2021 at 11:29:26AM +0200, Hannes Reinecke wrote:
> The serial number is copied into the buffer via memcpy_and_pad()
> with the length NVMET_SN_MAX_SIZE. So when printing out we also
> need to take just that length as anything beyond that will be
> uninitialized.
> 
> Signed-off-by: Hannes Reinecke <hare at suse.de>

The normal way to print a potentially unterminated fixed length string
would be something like:

diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c
index f74485c705ff2..d784f3c200b4c 100644
--- a/drivers/nvme/target/configfs.c
+++ b/drivers/nvme/target/configfs.c
@@ -1067,7 +1067,8 @@ static ssize_t nvmet_subsys_attr_serial_show(struct config_item *item,
 {
 	struct nvmet_subsys *subsys = to_subsys(item);
 
-	return snprintf(page, PAGE_SIZE, "%s\n", subsys->serial);
+	return snprintf(page, PAGE_SIZE, "%*s\n",
+			NVMET_SN_MAX_SIZE, subsys->serial);
 }
 
 static ssize_t