nvmet: prevent sprintf() overflow in nvmet_subsys_nsid_exists()

[ Upstream commit d15dcd0f1a4753b57e66c64c8dc2a9779ff96aab ]

The nsid value is a u32 that comes from nvmet_req_find_ns().  It's
endian data and we're on an error path and both of those raise red
flags.  So let's make this safer.

1) Make the buffer large enough for any u32.
2) Remove the unnecessary initialization.
3) Use snprintf() instead of sprintf() for even more safety.
4) The sprintf() function returns the number of bytes printed, not
   counting the NUL terminator. It is impossible for the return value to
   be <= 0 so delete that.

Fixes: 505363957fad ("nvmet: fix nvme status code when namespace is disabled")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c
index b7bfee4b77a845e602a65558c1cc2f41d4cb28b4..3ef6bc655661ddbab1b6bc950a660cd9bd03ab58 100644 (file)
--- a/drivers/nvme/target/configfs.c
+++ b/drivers/nvme/target/configfs.c
@@ -731,10 +731,9 @@ static struct configfs_attribute *nvmet_ns_attrs[] = {
 bool nvmet_subsys_nsid_exists(struct nvmet_subsys *subsys, u32 nsid)
 {
        struct config_item *ns_item;
-       char name[4] = {};
+       char name[12];
 
-       if (sprintf(name, "%u", nsid) <= 0)
-               return false;
+       snprintf(name, sizeof(name), "%u", nsid);
        mutex_lock(&subsys->namespaces_group.cg_subsys->su_mutex);
        ns_item = config_group_find_item(&subsys->namespaces_group, name);
        mutex_unlock(&subsys->namespaces_group.cg_subsys->su_mutex);