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Message-ID: <20070810072247.GB6639@localhost.sw.ru>
Date: Fri, 10 Aug 2007 11:22:48 +0400
From: Alexey Dobriyan <adobriyan@...ru>
To: akpm@...ux-foundation.org
Cc: linux-kernel@...r.kernel.org, ebiederm@...ssion.com
Subject: Re: + sysctl-factor-out-sysctl_data.patch added to -mm tree
On Thu, Aug 09, 2007 at 03:11:48PM -0700, akpm@...ux-foundation.org wrote:
> From: Eric W. Biederman <ebiederm@...ssion.com>
>
> There as been no easy way to wrap the default sysctl strategy routine except
> for returning 0. Which is not always what we want. The few instances I have
> seen that want different behaviour have written their own version of
> sysctl_data. While not too hard it is unnecessary code and has the potential
> for extra bugs.
>
> So to make these situations easier and make that part of sysctl more symetric
> I have factord sysctl_data out of do_sysctl_strategy and exported as a
> function everyone can use.
>
> Further having sysctl_data be an explicit function makes checking for badly
> formed sysctl tables much easier.
OK with idea, though naming sucks. generic_sysctl_strategy is much better.
> --- a/include/linux/sysctl.h~sysctl-factor-out-sysctl_data
> +++ a/include/linux/sysctl.h
> @@ -972,6 +972,7 @@ extern int do_sysctl_strategy (struct ct
> void __user *oldval, size_t __user *oldlenp,
> void __user *newval, size_t newlen);
>
> +extern ctl_handler sysctl_data;
> extern ctl_handler sysctl_string;
> extern ctl_handler sysctl_intvec;
> extern ctl_handler sysctl_jiffies;
> diff -puN kernel/sysctl.c~sysctl-factor-out-sysctl_data kernel/sysctl.c
> --- a/kernel/sysctl.c~sysctl-factor-out-sysctl_data
> +++ a/kernel/sysctl.c
> @@ -1457,7 +1457,6 @@ int do_sysctl_strategy (struct ctl_table
> void __user *newval, size_t newlen)
> {
> int op = 0, rc;
> - size_t len;
>
> if (oldval)
> op |= 004;
> @@ -1478,25 +1477,10 @@ int do_sysctl_strategy (struct ctl_table
> /* If there is no strategy routine, or if the strategy returns
> * zero, proceed with automatic r/w */
> if (table->data && table->maxlen) {
> - if (oldval && oldlenp) {
> - if (get_user(len, oldlenp))
> - return -EFAULT;
> - if (len) {
> - if (len > table->maxlen)
> - len = table->maxlen;
> - if(copy_to_user(oldval, table->data, len))
> - return -EFAULT;
> - if(put_user(len, oldlenp))
> - return -EFAULT;
> - }
> - }
> - if (newval && newlen) {
> - len = newlen;
> - if (len > table->maxlen)
> - len = table->maxlen;
> - if(copy_from_user(table->data, newval, len))
> - return -EFAULT;
> - }
> + rc = sysctl_data(table, name, nlen, oldval, oldlenp,
> + newval, newlen);
> + if (rc < 0)
> + return rc;
> }
> return 0;
> }
> @@ -2395,6 +2379,40 @@ int proc_doulongvec_ms_jiffies_minmax(st
> * General sysctl support routines
> */
>
> +/* The generic sysctl data routine (used if no strategy routine supplied) */
> +int sysctl_data(struct ctl_table *table, int __user *name, int nlen,
> + void __user *oldval, size_t __user *oldlenp,
> + void __user *newval, size_t newlen)
> +{
> + size_t len;
> +
> + /* Get out of I don't have a variable */
> + if (!table->data || !table->maxlen)
> + return -ENOTDIR;
> +
> + if (oldval && oldlenp) {
> + if (get_user(len, oldlenp))
> + return -EFAULT;
> + if (len) {
> + if (len > table->maxlen)
> + len = table->maxlen;
> + if (copy_to_user(oldval, table->data, len))
> + return -EFAULT;
> + if (put_user(len, oldlenp))
> + return -EFAULT;
> + }
> + }
> +
> + if (newval && newlen) {
> + if (newlen > table->maxlen)
> + newlen = table->maxlen;
> +
> + if (copy_from_user(table->data, newval, newlen))
> + return -EFAULT;
> + }
> + return 1;
> +}
> +
> /* The generic string strategy routine: */
> int sysctl_string(struct ctl_table *table, int __user *name, int nlen,
> void __user *oldval, size_t __user *oldlenp,
> @@ -2583,6 +2601,13 @@ out:
> return -ENOSYS;
> }
>
> +int sysctl_data(struct ctl_table *table, int __user *name, int nlen,
> + void __user *oldval, size_t __user *oldlenp,
> + void __user *newval, size_t newlen)
> +{
> + return -ENOSYS;
> +}
> +
> int sysctl_string(struct ctl_table *table, int __user *name, int nlen,
> void __user *oldval, size_t __user *oldlenp,
> void __user *newval, size_t newlen)
> @@ -2630,4 +2655,5 @@ EXPORT_SYMBOL(sysctl_intvec);
> EXPORT_SYMBOL(sysctl_jiffies);
> EXPORT_SYMBOL(sysctl_ms_jiffies);
> EXPORT_SYMBOL(sysctl_string);
> +EXPORT_SYMBOL(sysctl_data);
-
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