On Sat, 5 Apr 2014, Sasha Levin wrote:
> [ 1035.193166] Call Trace:
> [ 1035.193166] ? init_object (mm/slub.c:679)
> [ 1035.193166] setup_object.isra.34 (mm/slub.c:1071 mm/slub.c:1399)
> [ 1035.193166] new_slab (mm/slub.c:286 mm/slub.c:1439)
> [ 1035.193166] __slab_alloc (mm/slub.c:2203 mm/slub.c:2363)
> [ 1035.193166] ? kmem_cache_alloc (mm/slub.c:2469 mm/slub.c:2480
> mm/slub.c:2485)
Ok so the story here is that slub decided it needed a new slab and
requested memory from the page allocator.
setup_object() tries to write to the page which fails.
Could the page allocator have delivered a reference to a page struct that
creates an invalid address?
The code that fails is:
page = allocate_slab(s,
flags & (GFP_RECLAIM_MASK | GFP_CONSTRAINT_MASK), node);
if (!page)
goto out;
--- So we got a page from teh page allocator
order = compound_order(page);
inc_slabs_node(s, page_to_nid(page), page->objects);
memcg_bind_pages(s, order);
page->slab_cache = s;
__SetPageSlab(page);
-- Writing to the page struct works.
if (page->pfmemalloc)
SetPageSlabPfmemalloc(page);
start = page_address(page);
if (unlikely(s->flags & SLAB_POISON))
memset(start, POISON_INUSE, PAGE_SIZE << order);
--- This should have triggered since we write to the page but maybe this
slab has a ctor set and therefore no poisining is possible.
last = start;
for_each_object(p, s, start, page->objects) {
setup_object(s, page, last);
*** This is where the write access to the page fails.
set_freepointer(s, last, p);
last = p;
}
setup_object(s, page, last);
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