amd64/134786: [patch] vfs.bufspace sysctl wideness on amd64

[John Baldwin]

On Thursday 21 May 2009 10:48:25 am Emil Mikulic wrote:
> 
> >Number:         134786
> >Category:       amd64
> >Synopsis:       [patch] vfs.bufspace sysctl wideness on amd64
> >Confidential:   no
> >Severity:       non-critical
> >Priority:       low
> >Responsible:    freebsd-amd64
> >State:          open
> >Quarter:        
> >Keywords:       
> >Date-Required:
> >Class:          sw-bug
> >Submitter-Id:   current-users
> >Arrival-Date:   Thu May 21 14:50:04 UTC 2009
> >Closed-Date:
> >Last-Modified:
> >Originator:     Emil Mikulic
> >Release:        FreeBSD 8-CURRENT
> >Organization:
> >Environment:
> >Description:
> 
> On amd64, providing a 64-bit buffer to get the vfs.bufspace sysctl will
> return a 64-bit (long) quantity, but providing a *larger* buffer will
> only yield a 32-bit (int) quantity.
> 
> >How-To-Repeat:
> 
> len = 8;
> sysctlbyname("vfs.bufspace", &buf, &len, NULL, 0);
> /* len is still 8 */
> 
> len = 10;
> sysctlbyname("vfs.bufspace", &buf, &len, NULL, 0);
> /* len is 4! */
> 
> >Fix:
> 
> --- sys/kern/vfs_bio.c	2009-04-17 10:01:39.000000000 +0000
> +++ sys/kern/vfs_bio.c.2	2009-05-09 09:27:16.000000000 +0000
> @@ -288,15 +288,15 @@
>      defined(COMPAT_FREEBSD6) || defined(COMPAT_FREEBSD7)
>  static int
>  sysctl_bufspace(SYSCTL_HANDLER_ARGS)
>  {
>  	long lvalue;
>  	int ivalue;
>  
> -	if (sizeof(int) == sizeof(long) || req->oldlen == sizeof(long))
> +	if (sizeof(int) == sizeof(long) || req->oldlen >= sizeof(long))
>  		return (sysctl_handle_long(oidp, arg1, arg2, req));
>  	lvalue = *(long *)arg1;
>  	if (lvalue > INT_MAX)
>  		/* On overflow, still write out a long to trigger ENOMEM. */
>  		return (sysctl_handle_long(oidp, &lvalue, 0, req));
>  	ivalue = lvalue;
>  	return (sysctl_handle_int(oidp, &ivalue, 0, req));

Hummm.  I guess that is correct, though that is a bit odd.

-- 
John Baldwin