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authorPekka Enberg <penberg@cs.helsinki.fi>2006-06-23 02:03:40 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-06-23 07:42:51 -0700
commitddc2e812d592457747c4367fb73edcaa8e1e49ff (patch)
tree7dc9066c1e43d14f7c495847a9f0b24287806fb2
parent8d3c138b77f195ca0eee6fb639ae73f5ea9edb6b (diff)
[PATCH] slab: verify pointers before free
Passing an invalid pointer to kfree() and kmem_cache_free() is likely to cause bad memory corruption or even take down the whole system because the bad pointer is likely reused immediately due to the per-CPU caches. Until now, we don't do any verification for this if CONFIG_DEBUG_SLAB is disabled. As suggested by Linus, add PageSlab check to page_to_cache() and page_to_slab() to verify pointers passed to kfree(). Also, move the stronger check from cache_free_debugcheck() to kmem_cache_free() to ensure the passed pointer actually belongs to the cache we're about to free the object. For page_to_cache() and page_to_slab(), the assertions should have virtually no extra cost (two instructions, no data cache pressure) and for kmem_cache_free() the overhead should be minimal. Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi> Cc: Manfred Spraul <manfred@colorfullife.com> Cc: Christoph Lameter <clameter@engr.sgi.com> Cc: Linus Torvalds <torvalds@osdl.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--mm/slab.c13
1 files changed, 4 insertions, 9 deletions
diff --git a/mm/slab.c b/mm/slab.c
index 2046da2aa46..e3260db04b9 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -592,6 +592,7 @@ static inline struct kmem_cache *page_get_cache(struct page *page)
{
if (unlikely(PageCompound(page)))
page = (struct page *)page_private(page);
+ BUG_ON(!PageSlab(page));
return (struct kmem_cache *)page->lru.next;
}
@@ -604,6 +605,7 @@ static inline struct slab *page_get_slab(struct page *page)
{
if (unlikely(PageCompound(page)))
page = (struct page *)page_private(page);
+ BUG_ON(!PageSlab(page));
return (struct slab *)page->lru.prev;
}
@@ -2669,15 +2671,6 @@ static void *cache_free_debugcheck(struct kmem_cache *cachep, void *objp,
kfree_debugcheck(objp);
page = virt_to_page(objp);
- if (page_get_cache(page) != cachep) {
- printk(KERN_ERR "mismatch in kmem_cache_free: expected "
- "cache %p, got %p\n",
- page_get_cache(page), cachep);
- printk(KERN_ERR "%p is %s.\n", cachep, cachep->name);
- printk(KERN_ERR "%p is %s.\n", page_get_cache(page),
- page_get_cache(page)->name);
- WARN_ON(1);
- }
slabp = page_get_slab(page);
if (cachep->flags & SLAB_RED_ZONE) {
@@ -3393,6 +3386,8 @@ void kmem_cache_free(struct kmem_cache *cachep, void *objp)
{
unsigned long flags;
+ BUG_ON(virt_to_cache(objp) != cachep);
+
local_irq_save(flags);
__cache_free(cachep, objp);
local_irq_restore(flags);