Commit bc6697d8 authored by Eric Dumazet's avatar Eric Dumazet Committed by Pekka Enberg

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: default avatarChristoph Lameter <cl@linux.com>
Acked-by: default avatarDavid Rientjes <rientjes@google.com>
Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarPekka Enberg <penberg@kernel.org>
parent 42d623a8
......@@ -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) {
page = ACCESS_ONCE(c->page);
if (page) {
if (flags & SO_TOTAL)
x = c->page->objects;
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;
nodes[node] += x;
}
per_cpu[c->node]++;
per_cpu[node]++;
}
}
......
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