diff options
author | Christoph Lameter <cl@linux.com> | 2013-01-23 21:45:48 (GMT) |
---|---|---|
committer | Scott Wood <scottwood@freescale.com> | 2013-04-04 22:09:04 (GMT) |
commit | 3bc3e6047e6c95b221a7b8643a26525c3c9b5e55 (patch) | |
tree | 5ee0b1d3bf355ddbfd55a02bca110a9845a656d2 /mm | |
parent | f7b344595ee56ed4d9ae21873c96654ec60958f0 (diff) | |
download | linux-fsl-qoriq-3bc3e6047e6c95b221a7b8643a26525c3c9b5e55.tar.xz |
FIX [2/2] slub: Tid must be retrieved from the percpu area of the current processor
As Steven Rostedt has pointer out: Rescheduling could occur on a differnet processor
after the determination of the per cpu pointer and before the tid is retrieved.
This could result in allocation from the wrong node in slab_alloc.
The effect is much more severe in slab_free() where we could free to the freelist
of the wrong page.
The window for something like that occurring is pretty small but it is possible.
Signed-off-by: Christoph Lameter <cl@linux.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'mm')
-rw-r--r-- | mm/slub.c | 15 |
1 files changed, 8 insertions, 7 deletions
@@ -2331,13 +2331,13 @@ static __always_inline void *slab_alloc_node(struct kmem_cache *s, s = memcg_kmem_get_cache(s, gfpflags); redo: - /* - * Must read kmem_cache cpu data via this cpu ptr. Preemption is - * enabled. We may switch back and forth between cpus while - * reading from one cpu area. That does not matter as long - * as we end up on the original cpu again when doing the cmpxchg. + * Preemption is disabled for the retrieval of the tid because that + * must occur from the current processor. We cannot allow rescheduling + * on a different processor between the determination of the pointer + * and the retrieval of the tid. */ + preempt_disable(); c = __this_cpu_ptr(s->cpu_slab); /* @@ -2347,7 +2347,7 @@ redo: * linked list in between. */ tid = c->tid; - barrier(); + preempt_enable(); object = c->freelist; page = c->page; @@ -2594,10 +2594,11 @@ redo: * data is retrieved via this pointer. If we are on the same cpu * during the cmpxchg then the free will succedd. */ + preempt_disable(); c = __this_cpu_ptr(s->cpu_slab); tid = c->tid; - barrier(); + preempt_enable(); if (likely(page == c->page)) { set_freepointer(s, object, c->freelist); |