[PATCH v3 0/1] Fix object remain in offline per-cpu quarantine

[Kuan-Ying Lee]

This patch fixes object remain in the offline per-cpu quarantine as
describe below.

Free objects will get into per-cpu quarantine if enable generic KASAN.
If a cpu is offline and users use kmem_cache_destroy, kernel will detect
objects still remain in the offline per-cpu quarantine and report error.

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.

Changes since v3:
- Add a barrier to ensure the ordering
- Rename the init function

Changes since v2:
- Thanks for Dmitry suggestion
- Remove unnecessary code
- Put offline variable into cpu_quarantine
- Use single qlist_free_all call instead of iteration over all slabs
- Add bug reporter in commit message

Kuan-Ying Lee (1):
kasan: fix object remain in offline per-cpu quarantine

mm/kasan/quarantine.c | 40 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 40 insertions(+)

--
2.18.0

[Kuan-Ying Lee]

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-Y...@mediatek.com>
Suggested-by: Dmitry Vyukov <dvy...@google.com>
Reported-by: Guangye Yang <guangy...@mediatek.com>
Cc: Andrey Ryabinin <arya...@virtuozzo.com>
Cc: Alexander Potapenko <gli...@google.com>
Cc: Andrew Morton <ak...@linux-foundation.org>
Cc: Matthias Brugger <matthi...@gmail.com>
---

mm/kasan/quarantine.c | 40 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 40 insertions(+)

diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c
index 4c5375810449..cac7c617df72 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"
@@ -43,6 +44,7 @@ struct qlist_head {
struct qlist_node *head;
struct qlist_node *tail;
size_t bytes;
+ bool offline;
};

#define QLIST_INIT { NULL, NULL, 0 }
@@ -188,6 +190,11 @@ void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache)
local_irq_save(flags);

q = this_cpu_ptr(&cpu_quarantine);
+ if (q->offline) {
+ qlink_free(&info->quarantine_link, cache);
+ local_irq_restore(flags);
+ return;
+ }
qlist_put(q, &info->quarantine_link, cache->size);
if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) {
qlist_move_all(q, &temp);
@@ -328,3 +335,36 @@ void quarantine_remove_cache(struct kmem_cache *cache)

synchronize_srcu(&remove_cache_srcu);
}
+
+static int kasan_cpu_online(unsigned int cpu)
+{
+ this_cpu_ptr(&cpu_quarantine)->offline = false;
+ return 0;
+}
+
+static int kasan_cpu_offline(unsigned int cpu)
+{
+ struct qlist_head *q;
+
+ q = this_cpu_ptr(&cpu_quarantine);
+ /* Ensure the ordering between the writing to q->offline and
+ * qlist_free_all. Otherwise, cpu_quarantine may be corrupted
+ * by interrupt.
+ */
+ WRITE_ONCE(q->offline, true);
+ barrier();
+ qlist_free_all(q, NULL);
+ return 0;
+}
+
+static int __init kasan_cpu_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 < 0)
+ pr_err("kasan cpu quarantine register failed [%d]\n", ret);
+ return ret;
+}
+late_initcall(kasan_cpu_quarantine_init);
--
2.18.0

[Dmitry Vyukov]

Looks good to me, thanks.

Reviewed-by: Dmitry Vyukov <dvy...@google.com>

[Andrey Konovalov]

On Wed, Dec 2, 2020 at 8:58 AM Kuan-Ying Lee <Kuan-Y...@mediatek.com> wrote:
>

Hi Kuan-Ying,

This needs to be rebased onto the mm tree: it has some KASAN patches
that touch this code and rename the info variable to meta.

Thanks!

> --
> You received this message because you are subscribed to the Google Groups "kasan-dev" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+...@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/1606895585-17382-2-git-send-email-Kuan-Ying.Lee%40mediatek.com.

[Qian Cai]

On Wed, 2020-12-02 at 15:53 +0800, Kuan-Ying Lee wrote:
> 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.

Reverting this commit on the top of today's linux-next fixed memory corruptions
while doing CPU hotplug.

.config: https://cailca.coding.net/public/linux/mm/git/files/master/x86.config

[ 421.539476][ T120] BUG kmalloc-128 (Not tainted): Object already free
[ 421.546047][ T120] -----------------------------------------------------------------------------
[ 421.546047][ T120]
[ 421.557165][ T120] INFO: Allocated in memcg_alloc_page_obj_cgroups+0x86/0x140 age=755 cpu=21 pid=2316
[ 421.566533][ T120] __slab_alloc+0x55/0x70
[ 421.570744][ T120] __kmalloc_node+0xdc/0x280
[ 421.575215][ T120] memcg_alloc_page_obj_cgroups+0x86/0x140
[ 421.580910][ T120] allocate_slab+0xd8/0x610
[ 421.585299][ T120] ___slab_alloc+0x4cb/0x830
[ 421.589770][ T120] __slab_alloc+0x55/0x70
[ 421.593985][ T120] kmem_cache_alloc+0x225/0x280
[ 421.598724][ T120] vm_area_dup+0x76/0x2a0
[ 421.602940][ T120] __split_vma+0x90/0x4b0
[ 421.607151][ T120] mprotect_fixup+0x5da/0x7d0
[ 421.611712][ T120] do_mprotect_pkey+0x41a/0x7c0
[ 421.616447][ T120] __x64_sys_mprotect+0x74/0xb0
[ 421.621181][ T120] do_syscall_64+0x33/0x40
[ 421.625479][ T120] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 421.631262][ T120] INFO: Freed in quarantine_put+0xb5/0x1b0 age=3 cpu=21 pid=120
[ 421.638795][ T120] quarantine_put+0xe7/0x1b0
[ 421.643270][ T120] slab_free_freelist_hook+0x71/0x1a0
[ 421.648529][ T120] kfree+0xe2/0x5d0
[ 421.652215][ T120] __free_slab+0x1f8/0x300
[ 421.656517][ T120] qlist_free_all+0x56/0xc0
[ 421.660903][ T120] kasan_cpu_offline+0x1a/0x20
[ 421.665550][ T120] cpuhp_invoke_callback+0x1dd/0x1530
[ 421.670811][ T120] cpuhp_thread_fun+0x343/0x690
[ 421.675547][ T120] smpboot_thread_fn+0x30f/0x780
[ 421.680371][ T120] kthread+0x359/0x420
[ 421.684317][ T120] ret_from_fork+0x22/0x30
[ 421.688616][ T120] INFO: Slab 0x0000000080d42669 objects=12 used=11 fp=0x000000000ce8ce1d flags=0x4bfffc000010201
[ 421.699031][ T120] INFO: Object 0x000000000ce8ce1d @offset=1408 fp=0x0000000000000000
[ 421.699031][ T120]
[ 421.709186][ T120] Redzone 000000002d1421b0: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb ................
[ 421.719339][ T120] Redzone 0000000018565a7c: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb ................
[ 421.729492][ T120] Redzone 00000000d8a699c9: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb ................
[ 421.739645][ T120] Redzone 00000000af065f39: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb ................
[ 421.749800][ T120] Redzone 00000000480c8db9: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb ................
[ 421.759954][ T120] Redzone 00000000c37ee06b: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb ................
[ 421.770106][ T120] Redzone 0000000040f9cbf1: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb ................
[ 421.780256][ T120] Redzone 00000000e714e01e: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb ................
[ 421.790408][ T120] Object 000000000ce8ce1d: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
[ 421.800471][ T120] Object 0000000046eb4462: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
[ 421.810536][ T120] Object 00000000c3a122ae: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
[ 421.820599][ T120] Object 00000000d0195822: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
[ 421.830665][ T120] Object 000000008332e5f7: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
[ 421.840729][ T120] Object 00000000a04f77eb: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
[ 421.850796][ T120] Object 00000000326e9ce3: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
[ 421.860862][ T120] Object 00000000fa32b4b7: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b a5 kkkkkkkkkkkkkkk.
[ 421.870926][ T120] Redzone 000000001d59aa8f: bb bb bb bb bb bb bb bb ........
[ 421.880382][ T120] Padding 00000000f49e6727: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZZZZZ
[ 421.890537][ T120] Padding 000000007eb7befd: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZZZZZ
[ 421.900691][ T120] Padding 00000000c69f7c35: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZZZZZ
[ 421.910842][ T120] CPU: 21 PID: 120 Comm: cpuhp/21 Tainted: G B 5.10.0-rc6-next-20201203+ #8
[ 421.920733][ T120] Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 07/10/2019
[ 421.930011][ T120] Call Trace:
[ 421.933174][ T120] dump_stack+0x99/0xcb
[ 421.937210][ T120] free_debug_processing.cold.98+0x6a/0x111
[ 421.942993][ T120] ? __free_slab+0x1f8/0x300
[ 421.947467][ T120] ? __free_slab+0x1f8/0x300
[ 421.951942][ T120] __slab_free+0x302/0x560
[ 421.956241][ T120] ? lockdep_hardirqs_on_prepare+0x27c/0x3d0
[ 421.962110][ T120] ? quarantine_put+0x10a/0x1b0
[ 421.966846][ T120] ? trace_hardirqs_on+0x1c/0x150
[ 421.971754][ T120] ? slab_free_freelist_hook+0x71/0x1a0
[ 421.977192][ T120] kfree+0x595/0x5d0
[ 421.980967][ T120] ? __free_slab+0x1f8/0x300
[ 421.985439][ T120] __free_slab+0x1f8/0x300
[ 421.989738][ T120] ? qlist_free_all+0x2f/0xc0
[ 421.994299][ T120] qlist_free_all+0x56/0xc0
[ 421.998684][ T120] ? qlist_free_all+0xc0/0xc0
[ 422.003244][ T120] kasan_cpu_offline+0x1a/0x20
[ 422.007893][ T120] cpuhp_invoke_callback+0x1dd/0x1530
[ 422.013152][ T120] cpuhp_thread_fun+0x343/0x690
[ 422.017887][ T120] ? __cpuhp_state_remove_instance+0x490/0x490
[ 422.023934][ T120] smpboot_thread_fn+0x30f/0x780
[ 422.028756][ T120] ? smpboot_register_percpu_thread+0x370/0x370
[ 422.034888][ T120] ? trace_hardirqs_on+0x1c/0x150
[ 422.039800][ T120] ? __kthread_parkme+0xd1/0x1a0
[ 422.044622][ T120] ? smpboot_register_percpu_thread+0x370/0x370
[ 422.050753][ T120] kthread+0x359/0x420
[ 422.054704][ T120] ? kthread_create_on_node+0xc0/0xc0
[ 422.059965][ T120] ret_from_fork+0x22/0x30

[Andrew Morton]

On Thu, 3 Dec 2020 13:46:59 +0100 Andrey Konovalov <andre...@google.com> wrote:

> > #define QLIST_INIT { NULL, NULL, 0 }
> > @@ -188,6 +190,11 @@ void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache)
> > local_irq_save(flags);
> >
> > q = this_cpu_ptr(&cpu_quarantine);
> > + if (q->offline) {
> > + qlink_free(&info->quarantine_link, cache);
>
> Hi Kuan-Ying,
>
> This needs to be rebased onto the mm tree: it has some KASAN patches
> that touch this code and rename the info variable to meta.

Yup. I'm taking care of that.

[Kuan-Ying Lee]

Hi Andrew,

Sorry about that.
I will fix that conflict.

Thanks.

[Kuan-Ying Lee]

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.

Signed-off-by: Zqiang <qiang...@windriver.com>

Suggested-by: Dmitry Vyukov <dvy...@google.com>
Reported-by: Guangye Yang <guangy...@mediatek.com>

Reviewed-by: Dmitry Vyukov <dvy...@google.com>

Cc: Andrey Ryabinin <arya...@virtuozzo.com>
Cc: Alexander Potapenko <gli...@google.com>
Cc: Andrew Morton <ak...@linux-foundation.org>
Cc: Matthias Brugger <matthi...@gmail.com>

Cc: Andrey Konovalov <andre...@google.com>
Cc: Nicholas Tang <nichol...@mediatek.com>
Cc: Miles Chen <miles...@mediatek.com>
Cc: Qian Cai <qc...@redhat.com>
Cc: Stephen Rothwell <s...@canb.auug.org.au>
---
mm/kasan/quarantine.c | 39 +++++++++++++++++++++++++++++++++++++++
1 file changed, 39 insertions(+)

diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c
index a598c3514e1a..55783125a767 100644
--- a/mm/kasan/quarantine.c
+++ b/mm/kasan/quarantine.c
@@ -19,6 +19,7 @@

#include <linux/srcu.h>
#include <linux/string.h>
#include <linux/types.h>
+#include <linux/cpuhotplug.h>

#include "../slab.h"
#include "kasan.h"

@@ -33,6 +34,7 @@ struct qlist_head {

struct qlist_node *head;
struct qlist_node *tail;
size_t bytes;
+ bool offline;
};

#define QLIST_INIT { NULL, NULL, 0 }

@@ -191,6 +193,10 @@ bool quarantine_put(struct kmem_cache *cache, void *object)

local_irq_save(flags);

q = this_cpu_ptr(&cpu_quarantine);
+ if (q->offline) {

+ local_irq_restore(flags);
+ return false;
+ }
qlist_put(q, &meta->quarantine_link, cache->size);

if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) {
qlist_move_all(q, &temp);

@@ -333,3 +339,36 @@ void quarantine_remove_cache(struct kmem_cache *cache)

--
2.18.0

[Kuan-Ying Lee]

This patch fixes object remain in the offline per-cpu quarantine as
describe below.

Free objects will get into per-cpu quarantine if enable generic KASAN.
If a cpu is offline and users use kmem_cache_destroy, kernel will detect

objects still remain in the offline per-cpu quarantine and report error.

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.

Changes since v4:
- Rebase to linux-next
- Remove the qlist_free for double free issue
- Thanks Qiang, Qian

Changes since v3:
- Add a barrier to ensure the ordering
- Rename the init function

Changes since v2:
- Thanks for Dmitry suggestion
- Remove unnecessary code
- Put offline variable into cpu_quarantine
- Use single qlist_free_all call instead of iteration over all slabs
- Add bug reporter in commit message

Kuan-Ying Lee (1):
kasan: fix object remain in offline per-cpu quarantine

mm/kasan/quarantine.c | 39 +++++++++++++++++++++++++++++++++++++++
1 file changed, 39 insertions(+)

--
2.18.0