From bc6697d8a506dedf09e8e9974ffa3a316183e608 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 22 Nov 2011 16:02:02 +0100 Subject: [PATCH] slub: avoid potential NULL dereference or corruption show_slab_objects() can trigger NULL dereferences or memory corruption. Another cpu can change its c->page to NULL or c->node to NUMA_NO_NODE while we use them. Use ACCESS_ONCE(c->page) and ACCESS_ONCE(c->node) to make sure this cannot happen. Acked-by: Christoph Lameter Acked-by: David Rientjes Signed-off-by: Eric Dumazet Signed-off-by: Pekka Enberg --- mm/slub.c | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-) diff --git a/mm/slub.c b/mm/slub.c index 2a9cfd72a3d7..ed3334d9b6da 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -4444,30 +4444,31 @@ static ssize_t show_slab_objects(struct kmem_cache *s, for_each_possible_cpu(cpu) { struct kmem_cache_cpu *c = per_cpu_ptr(s->cpu_slab, cpu); + int node = ACCESS_ONCE(c->node); struct page *page; - if (!c || c->node < 0) + if (node < 0) continue; - - if (c->page) { - if (flags & SO_TOTAL) - x = c->page->objects; + page = ACCESS_ONCE(c->page); + if (page) { + if (flags & SO_TOTAL) + x = page->objects; else if (flags & SO_OBJECTS) - x = c->page->inuse; + x = page->inuse; else x = 1; total += x; - nodes[c->node] += x; + nodes[node] += x; } page = c->partial; if (page) { x = page->pobjects; - total += x; - nodes[c->node] += x; + total += x; + nodes[node] += x; } - per_cpu[c->node]++; + per_cpu[node]++; } } -- 2.30.2