[PATCH] nvmet: prevent sprintf() overflow in nvmet_subsys_nsid_exists()

[PATCH] nvmet: prevent sprintf() overflow in nvmet_subsys_nsid_exists()

[Dan Carpenter]

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>
---
 drivers/nvme/target/configfs.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c
index 89a001101a7f..37cd75ff150e 100644
--- 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);
-- 
2.43.0

Re: [PATCH] nvmet: prevent sprintf() overflow in nvmet_subsys_nsid_exists()

[Sagi Grimberg]

On 08/05/2024 10:43, Dan Carpenter wrote:
> 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>

Re: [PATCH] nvmet: prevent sprintf() overflow in nvmet_subsys_nsid_exists()

[Keith Busch]

On Wed, May 08, 2024 at 10:43:04AM +0300, Dan Carpenter wrote:
> 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>

Thanks, applied to nvme-6.9.