linux-kernel - Re: [PATCH 1/1] kernel/ucounts: expose current inotify watch count

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Message-ID: <20190122103529.GB13149@quack2.suse.cz>
Date:   Tue, 22 Jan 2019 11:35:29 +0100
From:   Jan Kara <jack@...e.cz>
To:     Albert Vaca Cintora <albertvaka@...il.com>
Cc:     jack@...e.cz, ebiederm@...ssion.com, linux-kernel@...r.kernel.org,
        nsaenzjulienne@...e.de
Subject: Re: [PATCH 1/1] kernel/ucounts: expose current inotify watch count

On Mon 21-01-19 17:45:11, Albert Vaca Cintora wrote:
> Adds a readonly 'current_inotify_watches' entry to the user sysctl table.
> The handler for this entry is a custom function that ends calling
> proc_dointvec.
> 
> Signed-off-by: Albert Vaca Cintora <albertvaka@...il.com>

FWIW this makes sense to me. I'd just copy a lot of the rationale from the
cover latter to this commit log so that it gets preseved in git history.
Other than that feel free to add:

Acked-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  kernel/ucount.c | 29 +++++++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
> 
> diff --git a/kernel/ucount.c b/kernel/ucount.c
> index f48d1b6376a4..afa3b89e3373 100644
> --- a/kernel/ucount.c
> +++ b/kernel/ucount.c
> @@ -57,6 +57,11 @@ static struct ctl_table_root set_root = {
>  	.permissions = set_permissions,
>  };
> 
> +#ifdef CONFIG_INOTIFY_USER
> +int proc_read_inotify_watches(struct ctl_table *table, int write,
> +		     void __user *buffer, size_t *lenp, loff_t *ppos);
> +#endif
> +
>  static int zero = 0;
>  static int int_max = INT_MAX;
>  #define UCOUNT_ENTRY(name)				\
> @@ -79,6 +84,12 @@ static struct ctl_table user_table[] = {
>  #ifdef CONFIG_INOTIFY_USER
>  	UCOUNT_ENTRY("max_inotify_instances"),
>  	UCOUNT_ENTRY("max_inotify_watches"),
> +	{
> +		.procname	= "current_inotify_watches",
> +		.maxlen		= sizeof(int),
> +		.mode		= 0444,
> +		.proc_handler	= proc_read_inotify_watches,
> +	},
>  #endif
>  	{ }
>  };
> @@ -226,6 +237,24 @@ void dec_ucount(struct ucounts *ucounts, enum ucount_type type)
>  	put_ucounts(ucounts);
>  }
> 
> +#ifdef CONFIG_INOTIFY_USER
> +int proc_read_inotify_watches(struct ctl_table *table, int write,
> +		     void __user *buffer, size_t *lenp, loff_t *ppos)
> +{
> +	struct ucounts *ucounts;
> +	struct ctl_table fake_table;
> +	int count;
> +
> +	ucounts = get_ucounts(current_user_ns(), current_euid());
> +	count = atomic_read(&ucounts->ucount[UCOUNT_INOTIFY_WATCHES]);
> +	put_ucounts(ucounts);
> +
> +	fake_table.data = &count;
> +	fake_table.maxlen = sizeof(count);
> +	return proc_dointvec(&fake_table, write, buffer, lenp, ppos);
> +}
> +#endif
> +
>  static __init int user_namespace_sysctl_init(void)
>  {
>  #ifdef CONFIG_SYSCTL
> --
> 2.20.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR