[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20110719065322.GA3228@albatros>
Date: Tue, 19 Jul 2011 10:53:22 +0400
From: Vasiliy Kulikov <segoon@...nwall.com>
To: Christoph Lameter <cl@...ux.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
kernel-hardening@...ts.openwall.com,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
x86@...nel.org, Arnd Bergmann <arnd@...db.de>,
Pekka Enberg <penberg@...nel.org>, Matt Mackall <mpm@...enic.com>,
Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
linux-mm@...ck.org
Subject: Re: [RFC v2] implement SL*B and stack usercopy runtime checks
On Mon, Jul 18, 2011 at 16:18 -0500, Christoph Lameter wrote:
> On Mon, 18 Jul 2011, Vasiliy Kulikov wrote:
>
> > --- a/mm/slab.c
> > +++ b/mm/slab.c
> > @@ -3844,6 +3844,40 @@ unsigned int kmem_cache_size(struct kmem_cache *cachep)
> > EXPORT_SYMBOL(kmem_cache_size);
> >
> > /*
> > + * Returns false if and only if [ptr; ptr+len) touches the slab,
> > + * but breaks objects boundaries. It doesn't check whether the
> > + * accessed object is actually allocated.
> > + */
> > +bool slab_access_ok(const void *ptr, unsigned long len)
> > +{
> > + struct page *page;
> > + struct kmem_cache *cachep = NULL;
>
> Why = NULL?
Indeed, redundant.
> > + struct slab *slabp;
> > + unsigned int objnr;
> > + unsigned long offset;
> > +
> > + if (!len)
> > + return true;
> > + if (!virt_addr_valid(ptr))
> > + return true;
> > + page = virt_to_head_page(ptr);
> > + if (!PageSlab(page))
> > + return true;
> > +
> > + cachep = page_get_cache(page);
> > + slabp = page_get_slab(page);
> > + objnr = obj_to_index(cachep, slabp, (void *)ptr);
> > + BUG_ON(objnr >= cachep->num);
> > + offset = (const char *)ptr - obj_offset(cachep) -
> > + (const char *)index_to_obj(cachep, slabp, objnr);
> > + if (offset <= obj_size(cachep) && len <= obj_size(cachep) - offset)
> > + return true;
> > +
> > + return false;
> > +}
> > +EXPORT_SYMBOL(slab_access_ok);
> > +
> > +/*
> > * This initializes kmem_list3 or resizes various caches for all nodes.
> > */
> > static int alloc_kmemlist(struct kmem_cache *cachep, gfp_t gfp)
>
> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -2623,6 +2623,34 @@ unsigned int kmem_cache_size(struct kmem_cache *s)
> > }
> > EXPORT_SYMBOL(kmem_cache_size);
> >
> > +/*
> > + * Returns false if and only if [ptr; ptr+len) touches the slab,
> > + * but breaks objects boundaries. It doesn't check whether the
> > + * accessed object is actually allocated.
> > + */
> > +bool slab_access_ok(const void *ptr, unsigned long len)
> > +{
> > + struct page *page;
> > + struct kmem_cache *s = NULL;
>
> No need to assign NULL.
Ditto.
> > + unsigned long offset;
> > +
> > + if (len == 0)
> > + return true;
> > + if (!virt_addr_valid(ptr))
> > + return true;
> > + page = virt_to_head_page(ptr);
> > + if (!PageSlab(page))
> > + return true;
> > +
> > + s = page->slab;
> > + offset = ((const char *)ptr - (const char *)page_address(page)) % s->size;
>
> Are the casts necessary? Both are pointers to void *
Is it normal kernel style to use void* pointer arithmetic?
> > + if (offset <= s->objsize && len <= s->objsize - offset)
>
> If offset == s->objsize then we access the first byte after the object.
Well, then objsize - offset == 0 and len can be 0 only to pass the right
part of && check. But (len == 0) case is already handled above.
But yes, for better readability it should be "<".
Thank you,
--
Vasiliy Kulikov
http://www.openwall.com - bringing security into open computing environments
Powered by blists - more mailing lists
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
