Re: [PATCH v2 8/8] FS: proc, make limits writable

From: Oleg Nesterov
Date: Fri Sep 04 2009 - 10:31:03 EST

On 09/03, Jiri Slaby wrote:
> Allow writing strings such as
> Max core file size=0:unlimited
> to /proc/<pid>/limits to change limits.

Can't review the parsing in limits_write() because I don't have enough
"C" skills, but otherwise the whole series looks correct to me.

One small nit, just to suggest the further 9/8 cleanup,

> +static const struct file_operations proc_pid_limits_operations = {
> + .read = proc_info_read,
> + .write = limits_write,
> +};

I think it makes sense to tweak proc_pid_limits() a little bit (and
rename it), so that we can do

.read = limits_read,
.write = limits_write


> @@ -2501,7 +2571,9 @@ static const struct pid_entry tgid_base_stuff[] = {
> + &proc_pid_limits_operations,
> + { .proc_read = proc_pid_limits }),

We could use

REG("limits", S_IRUSR|S_IWUSR, &proc_pid_limits_operations),

instead, this looks a bit cleaner to me.

But as I said, we can do this later.

And another minor nit (just in case you will re-submit this series for
some reason). Perhaps the changelog in 6/8 should mention that we do
not do any security checks when tsk != current (without selinux). We
assume that either the caller is sys_setrlimit(), or the caller should
verify it has rights to change the limits: in case of limits_write()
we rely on ->mode = S_IRUSR|S_IWUSR.


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