Re: [PATCH v2 2/4] nvme: reject invalid pr_read_keys() num_keys values

Christoph Hellwig
2025-12-01T06:36:54Z

On Thu, Nov 27, 2025 at 10:54:22AM -0500, Stefan Hajnoczi wrote:
> The pr_read_keys() interface has a u32 num_keys parameter. The NVMe
> Reservation Report command has a u32 maximum length. Reject num_keys
> values that are too large to fit.
>
> This will become important when pr_read_keys() is exposed to untrusted
> userspace via an <linux/pr.h> ioctl.
>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
> drivers/nvme/host/pr.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/nvme/host/pr.c b/drivers/nvme/host/pr.c
> index ca6a74607b139..156a2ae1fac2e 100644
> --- a/drivers/nvme/host/pr.c
> +++ b/drivers/nvme/host/pr.c
> @@ -233,6 +233,10 @@ static int nvme_pr_read_keys(struct block_device *bdev,
> int ret, i;
> bool eds;
>
> + /* Check that keys fit into u32 rse_len */
> + if (num_keys > (U32_MAX - sizeof(*rse)) / sizeof(rse->regctl_eds[0]))
> + return -EINVAL;
> +

We use struct_size to calculate the size below, which saturates on
overflow. So just checking the rse_len variable returned by the that
would be nicer. Bonus points for using sizeof_field() instead of
hardcoding U32_MAX.