Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758368Ab0KPOXt (ORCPT ); Tue, 16 Nov 2010 09:23:49 -0500 Received: from ipmail05.adl6.internode.on.net ([150.101.137.143]:2280 "EHLO ipmail05.adl6.internode.on.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755557Ab0KPOXq (ORCPT ); Tue, 16 Nov 2010 09:23:46 -0500 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AiQJAKMh4kx5Ldur/2dsb2JhbACVYYx9cr5mhUsEiliFEA Message-Id: <20101116142028.362270680@kernel.dk> User-Agent: quilt/0.48-1 Date: Wed, 17 Nov 2010 01:09:02 +1100 From: Nick Piggin To: linux-fsdevel@vger.kernel.org Cc: linux-kernel@vger.kernel.org Subject: [patch 02/28] kernel: kmem_ptr_validate considered harmful References: <20101116140900.039761100@kernel.dk> Content-Disposition: inline; filename=dcache-d_validate-broken.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6052 Lines: 189 This is a nasty ugly and error prone API. It's sole user, dcache, could not get it right so there is roughly zero chance that anything else will. Signed-off-by: Nick Piggin --- include/linux/slab.h | 2 -- mm/slab.c | 32 +------------------------------- mm/slob.c | 5 ----- mm/slub.c | 40 ---------------------------------------- mm/util.c | 21 --------------------- 5 files changed, 1 insertion(+), 99 deletions(-) Index: linux-2.6/include/linux/slab.h =================================================================== --- linux-2.6.orig/include/linux/slab.h 2010-11-17 00:10:41.000000000 +1100 +++ linux-2.6/include/linux/slab.h 2010-11-17 00:11:49.000000000 +1100 @@ -106,8 +106,6 @@ int kmem_cache_shrink(struct kmem_cache void kmem_cache_free(struct kmem_cache *, void *); unsigned int kmem_cache_size(struct kmem_cache *); const char *kmem_cache_name(struct kmem_cache *); -int kern_ptr_validate(const void *ptr, unsigned long size); -int kmem_ptr_validate(struct kmem_cache *cachep, const void *ptr); /* * Please use this macro to create slab caches. Simply specify the Index: linux-2.6/mm/slab.c =================================================================== --- linux-2.6.orig/mm/slab.c 2010-11-17 00:10:41.000000000 +1100 +++ linux-2.6/mm/slab.c 2010-11-17 00:11:49.000000000 +1100 @@ -2781,7 +2781,7 @@ static void slab_put_obj(struct kmem_cac /* * Map pages beginning at addr to the given cache and slab. This is required * for the slab allocator to be able to lookup the cache and slab of a - * virtual address for kfree, ksize, kmem_ptr_validate, and slab debugging. + * virtual address for kfree, ksize, and slab debugging. */ static void slab_map_pages(struct kmem_cache *cache, struct slab *slab, void *addr) @@ -3660,36 +3660,6 @@ void *kmem_cache_alloc_notrace(struct km EXPORT_SYMBOL(kmem_cache_alloc_notrace); #endif -/** - * kmem_ptr_validate - check if an untrusted pointer might be a slab entry. - * @cachep: the cache we're checking against - * @ptr: pointer to validate - * - * This verifies that the untrusted pointer looks sane; - * it is _not_ a guarantee that the pointer is actually - * part of the slab cache in question, but it at least - * validates that the pointer can be dereferenced and - * looks half-way sane. - * - * Currently only used for dentry validation. - */ -int kmem_ptr_validate(struct kmem_cache *cachep, const void *ptr) -{ - unsigned long size = cachep->buffer_size; - struct page *page; - - if (unlikely(!kern_ptr_validate(ptr, size))) - goto out; - page = virt_to_page(ptr); - if (unlikely(!PageSlab(page))) - goto out; - if (unlikely(page_get_cache(page) != cachep)) - goto out; - return 1; -out: - return 0; -} - #ifdef CONFIG_NUMA void *kmem_cache_alloc_node(struct kmem_cache *cachep, gfp_t flags, int nodeid) { Index: linux-2.6/mm/slub.c =================================================================== --- linux-2.6.orig/mm/slub.c 2010-11-17 00:10:41.000000000 +1100 +++ linux-2.6/mm/slub.c 2010-11-17 00:24:15.000000000 +1100 @@ -1917,17 +1917,6 @@ void kmem_cache_free(struct kmem_cache * } EXPORT_SYMBOL(kmem_cache_free); -/* Figure out on which slab page the object resides */ -static struct page *get_object_page(const void *x) -{ - struct page *page = virt_to_head_page(x); - - if (!PageSlab(page)) - return NULL; - - return page; -} - /* * Object placement in a slab is made very easy because we always start at * offset 0. If we tune the size of the object to the alignment then we can @@ -2386,35 +2375,6 @@ static int kmem_cache_open(struct kmem_c } /* - * Check if a given pointer is valid - */ -int kmem_ptr_validate(struct kmem_cache *s, const void *object) -{ - struct page *page; - - if (!kern_ptr_validate(object, s->size)) - return 0; - - page = get_object_page(object); - - if (!page || s != page->slab) - /* No slab or wrong slab */ - return 0; - - if (!check_valid_pointer(s, page, object)) - return 0; - - /* - * We could also check if the object is on the slabs freelist. - * But this would be too expensive and it seems that the main - * purpose of kmem_ptr_valid() is to check if the object belongs - * to a certain slab. - */ - return 1; -} -EXPORT_SYMBOL(kmem_ptr_validate); - -/* * Determine the size of a slab object */ unsigned int kmem_cache_size(struct kmem_cache *s) Index: linux-2.6/mm/util.c =================================================================== --- linux-2.6.orig/mm/util.c 2010-11-17 00:10:41.000000000 +1100 +++ linux-2.6/mm/util.c 2010-11-17 00:11:49.000000000 +1100 @@ -186,27 +186,6 @@ void kzfree(const void *p) } EXPORT_SYMBOL(kzfree); -int kern_ptr_validate(const void *ptr, unsigned long size) -{ - unsigned long addr = (unsigned long)ptr; - unsigned long min_addr = PAGE_OFFSET; - unsigned long align_mask = sizeof(void *) - 1; - - if (unlikely(addr < min_addr)) - goto out; - if (unlikely(addr > (unsigned long)high_memory - size)) - goto out; - if (unlikely(addr & align_mask)) - goto out; - if (unlikely(!kern_addr_valid(addr))) - goto out; - if (unlikely(!kern_addr_valid(addr + size - 1))) - goto out; - return 1; -out: - return 0; -} - /* * strndup_user - duplicate an existing string from user space * @s: The string to duplicate Index: linux-2.6/mm/slob.c =================================================================== --- linux-2.6.orig/mm/slob.c 2010-11-17 00:10:41.000000000 +1100 +++ linux-2.6/mm/slob.c 2010-11-17 00:11:49.000000000 +1100 @@ -678,11 +678,6 @@ int kmem_cache_shrink(struct kmem_cache } EXPORT_SYMBOL(kmem_cache_shrink); -int kmem_ptr_validate(struct kmem_cache *a, const void *b) -{ - return 0; -} - static unsigned int slob_ready __read_mostly; int slab_is_available(void) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/