Re: [PATCH 3/3] capabilities: add cap userns sysctl mask

[Tycho Andersen <tycho@tycho.pizza>]

Hi Jonathan,

On Thu, May 16, 2024 at 02:22:05AM -0700, Jonathan Calmels wrote:
> +int proc_cap_userns_handler(struct ctl_table *table, int write,
> +			    void *buffer, size_t *lenp, loff_t *ppos)
> +{

there is an ongoing effort (started at [0]) to constify the first arg
here, since you're not supposed to write to it. Your usage looks
correct to me, so I think all it needs is a literal "const" here.

[0]: https://lore.kernel.org/lkml/20240423-sysctl-const-handler-v3-0-e0beccb836e2@weissschuh.net/

> +	struct ctl_table t;
> +	unsigned long mask_array[2];
> +	kernel_cap_t new_mask, *mask;
> +	int err;
> +
> +	if (write && (!capable(CAP_SETPCAP) ||
> +		      !capable(CAP_SYS_ADMIN)))
> +		return -EPERM;

...why CAP_SYS_ADMIN? You mention it in the changelog, but don't
explain why.

Tycho