[RFC 2/2] Arch: Kconfig: Disable obsolete syscalls

[RFC 2/2] Arch: Kconfig: Disable obsolete syscalls

[Fabian Frederick]

fs: sysfs syscall: Disable if DISABLE_OBSOLETE_SYSCALLS

sysfs syscall is obsolete (cf man sysfs).

Don't define fs_index, fs_name, fs_maxindex functions when
DISABLE_OBSOLETE_SYSCALLS is defined.
In that case, SYSCALL_DEFINE3(sysfs...) returns automatically -EINVAL.

Signed-off-by: Fabian Frederick <fabf@skynet.be>
---
 fs/filesystems.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/filesystems.c b/fs/filesystems.c
index 92567d9..079626d 100644
--- a/fs/filesystems.c
+++ b/fs/filesystems.c
@@ -121,6 +121,7 @@ int unregister_filesystem(struct file_system_type * fs)
 
 EXPORT_SYMBOL(unregister_filesystem);
 
+#ifndef CONFIG_DISABLE_OBSOLETE_SYSCALLS
 static int fs_index(const char __user * __name)
 {
 	struct file_system_type * tmp;
@@ -199,6 +200,12 @@ SYSCALL_DEFINE3(sysfs, int, option, unsigned long, arg1, unsigned long, arg2)
 	}
 	return retval;
 }
+#else
+SYSCALL_DEFINE3(sysfs, int, option, unsigned long, arg1, unsigned long, arg2)
+{
+	return -EINVAL;
+}
+#endif /*CONFIG_DISABLE_OBSOLETE_SYSCALLS*/
 
 int __init get_filesystem_list(char *buf)
 {
-- 
1.8.1.4

Re: [RFC 2/2] Arch: Kconfig: Disable obsolete syscalls

[Andrew Morton]

On Wed, 12 Feb 2014 21:04:40 +0800 Fabian Frederick <fabf@skynet.be> wrote:

> fs: sysfs syscall: Disable if DISABLE_OBSOLETE_SYSCALLS
> 
> sysfs syscall is obsolete (cf man sysfs).
> 
> Don't define fs_index, fs_name, fs_maxindex functions when
> DISABLE_OBSOLETE_SYSCALLS is defined.
> In that case, SYSCALL_DEFINE3(sysfs...) returns automatically -EINVAL.
> 

Are there any other syscalls which will fall under
CONFIG_DISABLE_OBSOLETE_SYSCALLS?

There are plenty of other syscalls which can be disabled via Kconfig. 
As far as I recall, they each use their own CONFIG_foo.

So I'm thinking it would be better to add a CONFIG_SYS_SYSFS or
whatever which enables this syscall only.  It defaults to y.

> --- a/fs/filesystems.c
> +++ b/fs/filesystems.c
> @@ -121,6 +121,7 @@ int unregister_filesystem(struct file_system_type * fs)
>  
>  EXPORT_SYMBOL(unregister_filesystem);
>  
> +#ifndef CONFIG_DISABLE_OBSOLETE_SYSCALLS
>  static int fs_index(const char __user * __name)
>  {
>  	struct file_system_type * tmp;
> @@ -199,6 +200,12 @@ SYSCALL_DEFINE3(sysfs, int, option, unsigned long, arg1, unsigned long, arg2)
>  	}
>  	return retval;
>  }
> +#else
> +SYSCALL_DEFINE3(sysfs, int, option, unsigned long, arg1, unsigned long, arg2)
> +{
> +	return -EINVAL;
> +}
> +#endif /*CONFIG_DISABLE_OBSOLETE_SYSCALLS*/

And this should be done in kernel/sys_ni.c along with all the others.

Re: [RFC 2/2] Arch: Kconfig: Disable obsolete syscalls

[Fabian Frederick]

On Wed, 12 Feb 2014 13:13:14 -0800
Andrew Morton <akpm@linux-foundation.org> wrote:

> On Wed, 12 Feb 2014 21:04:40 +0800 Fabian Frederick <fabf@skynet.be> wrote:
> 
> > fs: sysfs syscall: Disable if DISABLE_OBSOLETE_SYSCALLS
> > 
> > sysfs syscall is obsolete (cf man sysfs).
> > 
> > Don't define fs_index, fs_name, fs_maxindex functions when
> > DISABLE_OBSOLETE_SYSCALLS is defined.
> > In that case, SYSCALL_DEFINE3(sysfs...) returns automatically -EINVAL.
> > 
> 
> Are there any other syscalls which will fall under
> CONFIG_DISABLE_OBSOLETE_SYSCALLS?
> 
> There are plenty of other syscalls which can be disabled via Kconfig. 
> As far as I recall, they each use their own CONFIG_foo.
> 
> So I'm thinking it would be better to add a CONFIG_SYS_SYSFS or
> whatever which enables this syscall only.  It defaults to y.

I thought it would be interesting to directly disable all of its but 
honestly I don't know if there are a lot so your solution seems interesting :)
Thanks for your help !

> 
> > --- a/fs/filesystems.c
> > +++ b/fs/filesystems.c
> > @@ -121,6 +121,7 @@ int unregister_filesystem(struct file_system_type * fs)
> >  
> >  EXPORT_SYMBOL(unregister_filesystem);
> >  
> > +#ifndef CONFIG_DISABLE_OBSOLETE_SYSCALLS
> >  static int fs_index(const char __user * __name)
> >  {
> >  	struct file_system_type * tmp;
> > @@ -199,6 +200,12 @@ SYSCALL_DEFINE3(sysfs, int, option, unsigned long, arg1, unsigned long, arg2)
> >  	}
> >  	return retval;
> >  }
> > +#else
> > +SYSCALL_DEFINE3(sysfs, int, option, unsigned long, arg1, unsigned long, arg2)
> > +{
> > +	return -EINVAL;
> > +}
> > +#endif /*CONFIG_DISABLE_OBSOLETE_SYSCALLS*/
> 
> And this should be done in kernel/sys_ni.c along with all the others.