nvmet: prevent sprintf() overflow in nvmet_subsys_nsid_exists()

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>

diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c
index 89a001101a7fca08bf047405aac92704bdd9a4c9..7fda69395c1ef80d319d5cefa70e6d5525db9bb3 100644 (file)
--- a/drivers/nvme/target/configfs.c
+++ b/drivers/nvme/target/configfs.c
@@ -757,10 +757,9 @@ 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);