Re: [PATCH] fix broken class-based syscall audit

[Eric Paris <eparis@redhat.com>]

On Mon, 2007-05-14 at 10:56 -0500, Klaus Weidner wrote:
> On Mon, May 14, 2007 at 05:51:50PM +0200, Marcus Meissner wrote:
> > On Mon, May 14, 2007 at 10:46:36AM -0500, Klaus Weidner wrote:
> > > The sanity check in audit_match_class() is wrong, AUDIT_BITMASK_SIZE is
> > > 64, providing space for 2048 syscalls in 64 * 32bit integers. The
> > > comparison only supports 256 syscalls (sizeof __u32 is 4), and silently
> > > returns "no match" for valid higher-numbered syscalls.
> [...]
> > > --- linux-2.6.18.i686/kernel/auditfilter.c.lspp.80	2007-05-11 17:06:08.000000000 -0500
> > > +++ linux-2.6.18.i686/kernel/auditfilter.c	2007-05-11 17:09:37.000000000 -0500
> > > @@ -306,7 +306,7 @@
> > >  
> > >  int audit_match_class(int class, unsigned syscall)
> > >  {
> > > -	if (unlikely(syscall >= AUDIT_BITMASK_SIZE * sizeof(__u32)))
> > > +	if (unlikely(syscall >= AUDIT_BITMASK_SIZE * 32))
> > >  		return 0;
> > >  	if (unlikely(class >= AUDIT_SYSCALL_CLASSES || !classes[class]))
> > >  		return 0;
> > 
> > You likely need to fix audit_register_class() if this is true.
> 
> I don't see a problem in audit_register_class() - it correctly uses
> sizeof(__u32) for allocating the memory since that's counted in bytes,
> only the comparison needs to count bits.

If that's the problem wouldn't we be better to use sizeof(__u32) *8
rather than hard code the 32 in there?  (sidebar: is it portable to
assume sizeof() returns bytes and *8 is the right way to go on all
archs?)  That would make it easier to do u32 search/replace in the
future if we ever have to grow this stuff....

-Eric