Re: [RFC v2] implement SL*B and stack usercopy runtime checks
From: Christoph Lameter <hidden>
Date: 2011-07-18 21:18:12
Also in:
linux-arch, lkml
On Mon, 18 Jul 2011, Vasiliy Kulikov wrote:
quoted hunk ↗ jump to hunk
--- 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?
+ 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)
quoted hunk ↗ jump to hunk
--- 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.
+ 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 *
+ if (offset <= s->objsize && len <= s->objsize - offset)
If offset == s->objsize then we access the first byte after the object. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>