From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Viro Subject: Re: [PATCH] fix broken class-based syscall audit Date: Tue, 15 May 2007 10:14:30 -0400 Message-ID: <20070515141430.GI27115@devserv.devel.redhat.com> References: <20070514154636.GA11536@w-m-p.com> <20070514155148.GB23829@suse.de> <20070514155608.GB11536@w-m-p.com> <1179175649.3964.5.camel@localhost.localdomain> <20070514213222.GC11536@w-m-p.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20070514213222.GC11536@w-m-p.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-audit-bounces@redhat.com Errors-To: linux-audit-bounces@redhat.com To: Klaus Weidner Cc: linux-audit@redhat.com List-Id: linux-audit@redhat.com On Mon, May 14, 2007 at 04:32:22PM -0500, Klaus Weidner wrote: > On Mon, May 14, 2007 at 04:47:29PM -0400, Eric Paris wrote: > > 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.... > > The AUDIT_WORD and AUDIT_BIT macros in include/linux/audit.h assume that > they'll fit 32 bits into each __u32: > > #define AUDIT_WORD(nr) ((__u32)((nr)/32)) > #define AUDIT_BIT(nr) (1 << ((nr) - AUDIT_WORD(nr)*32)) > > (If the actual capacity of the __u32 were larger they would continue > using only 32 bits.) > > I think the hardcoded 32 is appropriate. I'm not sure about the exact > sizeof() standard semantics, but I remember that the standard doesn't > assume 8-bit bytes. However, I think it's safe to assume that a __u32 > can fit 32 bits, if not a lot of other code would break also. Precisely. Nice catch and an obvious fix; patch from the beginning of this thread it can go to Linus right now. Acked-by: Al Viro (to match the signoff I'm normally using on kernel submits). Or I could pass it to Linus myself, if you wish.