diff options
author | Pekka Enberg <penberg@cs.helsinki.fi> | 2006-06-23 02:03:40 -0700 |
---|---|---|
committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-06-23 07:42:51 -0700 |
commit | ddc2e812d592457747c4367fb73edcaa8e1e49ff (patch) | |
tree | 7dc9066c1e43d14f7c495847a9f0b24287806fb2 /mm | |
parent | 8d3c138b77f195ca0eee6fb639ae73f5ea9edb6b (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>
Diffstat (limited to 'mm')
-rw-r--r-- | mm/slab.c | 13 |
1 files changed, 4 insertions, 9 deletions
diff --git a/mm/slab.c b/mm/slab.c index 2046da2aa46e..e3260db04b9e 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); |