[PATCH 1/1] kasan: fix object remain in offline per-cpu quarantine
Kuan-Ying Lee
Kuan-Ying.Lee at mediatek.com
Thu Nov 12 01:24:12 EST 2020
We hit this issue in our internal test.
When enabling generic kasan, a kfree()'d object is put into per-cpu
quarantine first. If the cpu goes offline, object still remains in
the per-cpu quarantine. If we call kmem_cache_destroy() now, slub
will report "Objects remaining" error.
[ 74.982625] =============================================================================
[ 74.983380] BUG test_module_slab (Not tainted): Objects remaining in test_module_slab on __kmem_cache_shutdown()
[ 74.984145] -----------------------------------------------------------------------------
[ 74.984145]
[ 74.984883] Disabling lock debugging due to kernel taint
[ 74.985561] INFO: Slab 0x(____ptrval____) objects=34 used=1 fp=0x(____ptrval____) flags=0x2ffff00000010200
[ 74.986638] CPU: 3 PID: 176 Comm: cat Tainted: G B 5.10.0-rc1-00007-g4525c8781ec0-dirty #10
[ 74.987262] Hardware name: linux,dummy-virt (DT)
[ 74.987606] Call trace:
[ 74.987924] dump_backtrace+0x0/0x2b0
[ 74.988296] show_stack+0x18/0x68
[ 74.988698] dump_stack+0xfc/0x168
[ 74.989030] slab_err+0xac/0xd4
[ 74.989346] __kmem_cache_shutdown+0x1e4/0x3c8
[ 74.989779] kmem_cache_destroy+0x68/0x130
[ 74.990176] test_version_show+0x84/0xf0
[ 74.990679] module_attr_show+0x40/0x60
[ 74.991218] sysfs_kf_seq_show+0x128/0x1c0
[ 74.991656] kernfs_seq_show+0xa0/0xb8
[ 74.992059] seq_read+0x1f0/0x7e8
[ 74.992415] kernfs_fop_read+0x70/0x338
[ 74.993051] vfs_read+0xe4/0x250
[ 74.993498] ksys_read+0xc8/0x180
[ 74.993825] __arm64_sys_read+0x44/0x58
[ 74.994203] el0_svc_common.constprop.0+0xac/0x228
[ 74.994708] do_el0_svc+0x38/0xa0
[ 74.995088] el0_sync_handler+0x170/0x178
[ 74.995497] el0_sync+0x174/0x180
[ 74.996050] INFO: Object 0x(____ptrval____) @offset=15848
[ 74.996752] INFO: Allocated in test_version_show+0x98/0xf0 age=8188 cpu=6 pid=172
[ 75.000802] stack_trace_save+0x9c/0xd0
[ 75.002420] set_track+0x64/0xf0
[ 75.002770] alloc_debug_processing+0x104/0x1a0
[ 75.003171] ___slab_alloc+0x628/0x648
[ 75.004213] __slab_alloc.isra.0+0x2c/0x58
[ 75.004757] kmem_cache_alloc+0x560/0x588
[ 75.005376] test_version_show+0x98/0xf0
[ 75.005756] module_attr_show+0x40/0x60
[ 75.007035] sysfs_kf_seq_show+0x128/0x1c0
[ 75.007433] kernfs_seq_show+0xa0/0xb8
[ 75.007800] seq_read+0x1f0/0x7e8
[ 75.008128] kernfs_fop_read+0x70/0x338
[ 75.008507] vfs_read+0xe4/0x250
[ 75.008990] ksys_read+0xc8/0x180
[ 75.009462] __arm64_sys_read+0x44/0x58
[ 75.010085] el0_svc_common.constprop.0+0xac/0x228
[ 75.011006] kmem_cache_destroy test_module_slab: Slab cache still has objects
Register a cpu hotplug function to remove all objects in the offline
per-cpu quarantine when cpu is going offline. Set a per-cpu variable
to indicate this cpu is offline.
Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee at mediatek.com>
---
mm/kasan/quarantine.c | 59 +++++++++++++++++++++++++++++++++++++++++--
1 file changed, 57 insertions(+), 2 deletions(-)
diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c
index 4c5375810449..67fb91ae2bd0 100644
--- a/mm/kasan/quarantine.c
+++ b/mm/kasan/quarantine.c
@@ -29,6 +29,7 @@
#include <linux/srcu.h>
#include <linux/string.h>
#include <linux/types.h>
+#include <linux/cpuhotplug.h>
#include "../slab.h"
#include "kasan.h"
@@ -97,6 +98,7 @@ static void qlist_move_all(struct qlist_head *from, struct qlist_head *to)
* guarded by quarantine_lock.
*/
static DEFINE_PER_CPU(struct qlist_head, cpu_quarantine);
+static DEFINE_PER_CPU(int, cpu_quarantine_offline);
/* Round-robin FIFO array of batches. */
static struct qlist_head global_quarantine[QUARANTINE_BATCHES];
@@ -176,6 +178,8 @@ void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache)
unsigned long flags;
struct qlist_head *q;
struct qlist_head temp = QLIST_INIT;
+ int *offline;
+ struct qlist_head q_offline = QLIST_INIT;
/*
* Note: irq must be disabled until after we move the batch to the
@@ -187,8 +191,16 @@ void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache)
*/
local_irq_save(flags);
- q = this_cpu_ptr(&cpu_quarantine);
- qlist_put(q, &info->quarantine_link, cache->size);
+ offline = this_cpu_ptr(&cpu_quarantine_offline);
+ if (*offline == 0) {
+ q = this_cpu_ptr(&cpu_quarantine);
+ qlist_put(q, &info->quarantine_link, cache->size);
+ } else {
+ qlist_put(&q_offline, &info->quarantine_link, cache->size);
+ qlist_free_all(&q_offline, cache);
+ local_irq_restore(flags);
+ return;
+ }
if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) {
qlist_move_all(q, &temp);
@@ -328,3 +340,46 @@ void quarantine_remove_cache(struct kmem_cache *cache)
synchronize_srcu(&remove_cache_srcu);
}
+
+static int kasan_cpu_online(unsigned int cpu)
+{
+ int *offline;
+ unsigned long flags;
+
+ local_irq_save(flags);
+ offline = this_cpu_ptr(&cpu_quarantine_offline);
+ *offline = 0;
+ local_irq_restore(flags);
+ return 0;
+}
+
+static int kasan_cpu_offline(unsigned int cpu)
+{
+ struct kmem_cache *s;
+ int *offline;
+ unsigned long flags;
+
+ local_irq_save(flags);
+ offline = this_cpu_ptr(&cpu_quarantine_offline);
+ *offline = 1;
+ local_irq_restore(flags);
+
+ mutex_lock(&slab_mutex);
+ list_for_each_entry(s, &slab_caches, list) {
+ per_cpu_remove_cache(s);
+ }
+ mutex_unlock(&slab_mutex);
+ return 0;
+}
+
+static int __init kasan_cpu_offline_quarantine_init(void)
+{
+ int ret = 0;
+
+ ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "mm/kasan:online",
+ kasan_cpu_online, kasan_cpu_offline);
+ if (ret)
+ pr_err("kasan offline cpu quarantine register failed [%d]\n", ret);
+ return ret;
+}
+late_initcall(kasan_cpu_offline_quarantine_init);
--
2.18.0
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