Re: [PATCH net-next v3 3/3] eventpoll: Add epoll ioctl for epoll_params

Greg Kroah-Hartman
2024-01-25T23:22:36Z

On Thu, Jan 25, 2024 at 10:56:59PM +0000, Joe Damato wrote:
> Add an ioctl for getting and setting epoll_params. User programs can use
> this ioctl to get and set the busy poll usec time or packet budget
> params for a specific epoll context.
>
> Signed-off-by: Joe Damato <jdamato@fastly.com>
> ---
> .../userspace-api/ioctl/ioctl-number.rst | 1 +
> fs/eventpoll.c | 64 +++++++++++++++++++
> include/uapi/linux/eventpoll.h | 12 ++++
> 3 files changed, 77 insertions(+)
>
> diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst
> index 457e16f06e04..b33918232f78 100644
> --- a/Documentation/userspace-api/ioctl/ioctl-number.rst
> +++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
> @@ -309,6 +309,7 @@ Code Seq# Include File Comments
> 0x89 0B-DF linux/sockios.h
> 0x89 E0-EF linux/sockios.h SIOCPROTOPRIVATE range
> 0x89 F0-FF linux/sockios.h SIOCDEVPRIVATE range
> +0x8A 00-1F linux/eventpoll.h
> 0x8B all linux/wireless.h
> 0x8C 00-3F WiNRADiO driver
> <http://www.winradio.com.au/>
> diff --git a/fs/eventpoll.c b/fs/eventpoll.c
> index 40bd97477b91..73ae886efb8a 100644
> --- a/fs/eventpoll.c
> +++ b/fs/eventpoll.c
> @@ -6,6 +6,8 @@
> * Davide Libenzi <davidel@xmailserver.org>
> */
>
> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> +
> #include <linux/init.h>
> #include <linux/kernel.h>
> #include <linux/sched/signal.h>
> @@ -37,6 +39,7 @@
> #include <linux/seq_file.h>
> #include <linux/compat.h>
> #include <linux/rculist.h>
> +#include <linux/capability.h>
> #include <net/busy_poll.h>
>
> /*
> @@ -495,6 +498,39 @@ static inline void ep_set_busy_poll_napi_id(struct epitem *epi)
> ep->napi_id = napi_id;
> }
>
> +static long ep_eventpoll_bp_ioctl(struct file *file, unsigned int cmd,
> + unsigned long arg)
> +{
> + struct eventpoll *ep;
> + struct epoll_params epoll_params;
> + void __user *uarg = (void __user *) arg;
> +
> + ep = file->private_data;
> +
> + switch (cmd) {
> + case EPIOCSPARAMS:
> + if (copy_from_user(&epoll_params, uarg, sizeof(epoll_params)))
> + return -EFAULT;
> +
> + if (epoll_params.busy_poll_budget > NAPI_POLL_WEIGHT &&
> + !capable(CAP_NET_ADMIN))
> + return -EPERM;
> +
> + ep->busy_poll_usecs = epoll_params.busy_poll_usecs;
> + ep->busy_poll_budget = epoll_params.busy_poll_budget;
> + return 0;
> + case EPIOCGPARAMS:
> + memset(&epoll_params, 0, sizeof(epoll_params));
> + epoll_params.busy_poll_usecs = ep->busy_poll_usecs;
> + epoll_params.busy_poll_budget = ep->busy_poll_budget;
> + if (copy_to_user(uarg, &epoll_params, sizeof(epoll_params)))
> + return -EFAULT;
> + return 0;
> + default:
> + return -ENOIOCTLCMD;
> + }
> +}
> +
> #else
>
> static inline bool ep_busy_loop(struct eventpoll *ep, int nonblock)
> @@ -510,6 +546,12 @@ static inline bool ep_busy_loop_on(struct eventpoll *ep)
> {
> return false;
> }
> +
> +static long ep_eventpoll_bp_ioctl(struct file *file, unsigned int cmd,
> + unsigned long arg)
> +{
> + return -EOPNOTSUPP;
> +}
> #endif /* CONFIG_NET_RX_BUSY_POLL */
>
> /*
> @@ -869,6 +911,26 @@ static void ep_clear_and_put(struct eventpoll *ep)
> ep_free(ep);
> }
>
> +static long ep_eventpoll_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> +{
> + int ret;
> +
> + if (!is_file_epoll(file))
> + return -EINVAL;
> +
> + switch (cmd) {
> + case EPIOCSPARAMS:
> + case EPIOCGPARAMS:
> + ret = ep_eventpoll_bp_ioctl(file, cmd, arg);
> + break;
> + default:
> + ret = -EINVAL;
> + break;
> + }
> +
> + return ret;
> +}
> +
> static int ep_eventpoll_release(struct inode *inode, struct file *file)
> {
> struct eventpoll *ep = file->private_data;
> @@ -975,6 +1037,8 @@ static const struct file_operations eventpoll_fops = {
> .release = ep_eventpoll_release,
> .poll = ep_eventpoll_poll,
> .llseek = noop_llseek,
> + .unlocked_ioctl = ep_eventpoll_ioctl,
> + .compat_ioctl = compat_ptr_ioctl,
> };
>
> /*
> diff --git a/include/uapi/linux/eventpoll.h b/include/uapi/linux/eventpoll.h
> index cfbcc4cc49ac..8eb0fdbce995 100644
> --- a/include/uapi/linux/eventpoll.h
> +++ b/include/uapi/linux/eventpoll.h
> @@ -85,4 +85,16 @@ struct epoll_event {
> __u64 data;
> } EPOLL_PACKED;
>
> +struct epoll_params {
> + u64 busy_poll_usecs;
> + u16 busy_poll_budget;
> +
> + /* for future fields */
> + u8 data[118];

You forgot to validate that "data" is set to 0, which means that this
would be useless. Why have this at all?

thanks,

greg k-h