On Wed, Feb 11, 2015 at 09:00:39AM -0600, Christoph Lameter wrote: > Hmmmm... Thinking about this some more. It may be better to initialize the > list head at the beginning of the loop? > > Also the promote array should also be initialized in the loop right?
I do initialize promote lists in the loop using list_splice_init, but yeah, initializing them in the beginning of the loop would look more readable indeed. The updated patch is below. Thanks! --- From: Vladimir Davydov <[email protected]> Subject: [PATCH] slub: kmem_cache_shrink: fix crash due to uninitialized discard list Currently, the discard list is only initialized at the beginning of the function. As a result, if there are > 1 nodes, we can get use-after-free while processing the second or higher node: WARNING: CPU: 60 PID: 1 at lib/list_debug.c:29 __list_add+0x3c/0xa9() list_add corruption. next->prev should be prev (ffff881ff0a6bb98), but was ffffea007ff57020. (next=ffffea007fbf7320). Modules linked in: CPU: 60 PID: 1 Comm: swapper/0 Not tainted 3.19.0-rc7-next-20150203-gb50cadf #2178 Hardware name: Intel Corporation BRICKLAND/BRICKLAND, BIOS BIVTSDP1.86B.0038.R02.1307231126 07/23/2013 0000000000000009 ffff881ff0a6ba88 ffffffff81c2e096 ffffffff810e2d03 ffff881ff0a6bad8 ffff881ff0a6bac8 ffffffff8108b320 ffff881ff0a6bb18 ffffffff8154bbc7 ffff881ff0a6bb98 ffffea007fbf7320 ffffea00ffc3c220 Call Trace: [<ffffffff81c2e096>] dump_stack+0x4c/0x65 [<ffffffff810e2d03>] ? console_unlock+0x398/0x3c7 [<ffffffff8108b320>] warn_slowpath_common+0xa1/0xbb [<ffffffff8154bbc7>] ? __list_add+0x3c/0xa9 [<ffffffff8108b380>] warn_slowpath_fmt+0x46/0x48 [<ffffffff8154bbc7>] __list_add+0x3c/0xa9 [<ffffffff811bf5aa>] __kmem_cache_shrink+0x12b/0x24c [<ffffffff81190ca9>] kmem_cache_shrink+0x26/0x38 [<ffffffff815848b4>] acpi_os_purge_cache+0xe/0x12 [<ffffffff815c6424>] acpi_purge_cached_objects+0x32/0x7a [<ffffffff825f70f1>] acpi_initialize_objects+0x17e/0x1ae [<ffffffff825f5177>] ? acpi_sleep_proc_init+0x2a/0x2a [<ffffffff825f5209>] acpi_init+0x92/0x25e [<ffffffff810002bd>] ? do_one_initcall+0x90/0x17f [<ffffffff811bdfcd>] ? kfree+0x1fc/0x2d5 [<ffffffff825f5177>] ? acpi_sleep_proc_init+0x2a/0x2a [<ffffffff8100031a>] do_one_initcall+0xed/0x17f [<ffffffff825ae0e2>] kernel_init_freeable+0x1f0/0x278 [<ffffffff81c1f31a>] ? rest_init+0x13e/0x13e [<ffffffff81c1f328>] kernel_init+0xe/0xda [<ffffffff81c3ca7c>] ret_from_fork+0x7c/0xb0 [<ffffffff81c1f31a>] ? rest_init+0x13e/0x13e Fix this by initializing the discard list at each iteration of the for_each_kmem_cache_node loop. Also, move promote lists initialization to the beginning of the loop to conform. fixes: slub-never-fail-to-shrink-cache Signed-off-by: Vladimir Davydov <[email protected]> Reported-by: Huang Ying <[email protected]> Cc: Christoph Lameter <[email protected]> Cc: Pekka Enberg <[email protected]> Cc: David Rientjes <[email protected]> Cc: Joonsoo Kim <[email protected]> diff --git a/mm/slub.c b/mm/slub.c index 0909e13cf708..6832c4eab104 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -3437,7 +3437,7 @@ int __kmem_cache_shrink(struct kmem_cache *s, bool deactivate) struct kmem_cache_node *n; struct page *page; struct page *t; - LIST_HEAD(discard); + struct list_head discard; struct list_head promote[SHRINK_PROMOTE_MAX]; unsigned long flags; int ret = 0; @@ -3457,11 +3457,12 @@ int __kmem_cache_shrink(struct kmem_cache *s, bool deactivate) kick_all_cpus_sync(); } - for (i = 0; i < SHRINK_PROMOTE_MAX; i++) - INIT_LIST_HEAD(promote + i); - flush_all(s); for_each_kmem_cache_node(s, node, n) { + INIT_LIST_HEAD(&discard); + for (i = 0; i < SHRINK_PROMOTE_MAX; i++) + INIT_LIST_HEAD(promote + i); + spin_lock_irqsave(&n->list_lock, flags); /* @@ -3491,7 +3492,7 @@ int __kmem_cache_shrink(struct kmem_cache *s, bool deactivate) * partial list. */ for (i = SHRINK_PROMOTE_MAX - 1; i >= 0; i--) - list_splice_init(promote + i, &n->partial); + list_splice(promote + i, &n->partial); spin_unlock_irqrestore(&n->list_lock, flags); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
