From bbd7d57bfe852d9788bae5fb171c7edb4021d8ac Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 24 Mar 2010 22:25:47 +0100 Subject: [PATCH] slub: Potential stack overflow I discovered that we can overflow stack if CONFIG_SLUB_DEBUG=y and use slabs with many objects, since list_slab_objects() and process_slab() use DECLARE_BITMAP(map, page->objects). With 65535 bits, we use 8192 bytes of stack ... Switch these allocations to dynamic allocations. Signed-off-by: Eric Dumazet Signed-off-by: Christoph Lameter Signed-off-by: Pekka Enberg --- mm/slub.c | 25 ++++++++++++++++--------- 1 file changed, 16 insertions(+), 9 deletions(-) diff --git a/mm/slub.c b/mm/slub.c index d2a54fe71ea2..78f1a202ca33 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2429,9 +2429,11 @@ static void list_slab_objects(struct kmem_cache *s, struct page *page, #ifdef CONFIG_SLUB_DEBUG void *addr = page_address(page); void *p; - DECLARE_BITMAP(map, page->objects); + long *map = kzalloc(BITS_TO_LONGS(page->objects) * sizeof(long), + GFP_ATOMIC); - bitmap_zero(map, page->objects); + if (!map) + return; slab_err(s, page, "%s", text); slab_lock(page); for_each_free_object(p, s, page->freelist) @@ -2446,6 +2448,7 @@ static void list_slab_objects(struct kmem_cache *s, struct page *page, } } slab_unlock(page); + kfree(map); #endif } @@ -3651,10 +3654,10 @@ static int add_location(struct loc_track *t, struct kmem_cache *s, } static void process_slab(struct loc_track *t, struct kmem_cache *s, - struct page *page, enum track_item alloc) + struct page *page, enum track_item alloc, + long *map) { void *addr = page_address(page); - DECLARE_BITMAP(map, page->objects); void *p; bitmap_zero(map, page->objects); @@ -3673,11 +3676,14 @@ static int list_locations(struct kmem_cache *s, char *buf, unsigned long i; struct loc_track t = { 0, 0, NULL }; int node; + unsigned long *map = kmalloc(BITS_TO_LONGS(oo_objects(s->max)) * + sizeof(unsigned long), GFP_KERNEL); - if (!alloc_loc_track(&t, PAGE_SIZE / sizeof(struct location), - GFP_TEMPORARY)) + if (!map || !alloc_loc_track(&t, PAGE_SIZE / sizeof(struct location), + GFP_TEMPORARY)) { + kfree(map); return sprintf(buf, "Out of memory\n"); - + } /* Push back cpu slabs */ flush_all(s); @@ -3691,9 +3697,9 @@ static int list_locations(struct kmem_cache *s, char *buf, spin_lock_irqsave(&n->list_lock, flags); list_for_each_entry(page, &n->partial, lru) - process_slab(&t, s, page, alloc); + process_slab(&t, s, page, alloc, map); list_for_each_entry(page, &n->full, lru) - process_slab(&t, s, page, alloc); + process_slab(&t, s, page, alloc, map); spin_unlock_irqrestore(&n->list_lock, flags); } @@ -3744,6 +3750,7 @@ static int list_locations(struct kmem_cache *s, char *buf, } free_loc_track(&t); + kfree(map); if (!t.count) len += sprintf(buf, "No data\n"); return len;