2.6.39-stable review patch. If anyone has any objections, please let us know.
------------------ Content-Length: 1498 Lines: 50 From: Christoph Lameter <[email protected]> commit 1393d9a1857471f816d0be1ccc1d6433a86050f6 upstream. Fastpath can do a speculative access to a page that CONFIG_DEBUG_PAGE_ALLOC may have marked as invalid to retrieve the pointer to the next free object. Use probe_kernel_read in that case in order not to cause a page fault. Reported-by: Eric Dumazet <[email protected]> Signed-off-by: Christoph Lameter <[email protected]> Signed-off-by: Eric Dumazet <[email protected]> Signed-off-by: Pekka Enberg <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- mm/slub.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) --- a/mm/slub.c +++ b/mm/slub.c @@ -261,6 +261,18 @@ static inline void *get_freepointer(stru return *(void **)(object + s->offset); } +static inline void *get_freepointer_safe(struct kmem_cache *s, void *object) +{ + void *p; + +#ifdef CONFIG_DEBUG_PAGEALLOC + probe_kernel_read(&p, (void **)(object + s->offset), sizeof(p)); +#else + p = get_freepointer(s, object); +#endif + return p; +} + static inline void set_freepointer(struct kmem_cache *s, void *object, void *fp) { *(void **)(object + s->offset) = fp; @@ -1943,7 +1955,7 @@ redo: if (unlikely(!irqsafe_cpu_cmpxchg_double( s->cpu_slab->freelist, s->cpu_slab->tid, object, tid, - get_freepointer(s, object), next_tid(tid)))) { + get_freepointer_safe(s, object), next_tid(tid)))) { note_cmpxchg_failure("slab_alloc", s, tid); goto redo; _______________________________________________ stable mailing list [email protected] http://linux.kernel.org/mailman/listinfo/stable
