| Message ID | 1605508168-7418-2-git-send-email-Kuan-Ying.Lee@mediatek.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Fix object remain in offline per-cpu quarantine | expand |
On Mon, Nov 16, 2020 at 7:30 AM Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com> 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. > > [ 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@mediatek.com> > Suggested-by: Dmitry Vyukov <dvyukov@google.com> > Reported-by: Guangye Yang <guangye.yang@mediatek.com> > Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> > Cc: Alexander Potapenko <glider@google.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Matthias Brugger <matthias.bgg@gmail.com> > --- > mm/kasan/quarantine.c | 35 +++++++++++++++++++++++++++++++++++ > 1 file changed, 35 insertions(+) > > diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c > index 4c5375810449..16e618ea805e 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 +335,31 @@ 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); > + q->offline = true; > + qlist_free_all(q, NULL); Looks much nicer now! What is the story with interrupts in these callbacks? In the previous patch you mentioned that this CPU can still receive interrupts for a brief period of time. If these interrupts also free something, can't we corrupt the per-cpu quarantine? In quarantine_put we protect it by disabling interrupts I think. > + 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 < 0) > + pr_err("kasan offline cpu quarantine register failed [%d]\n", ret); > + return ret; > +} > +late_initcall(kasan_cpu_offline_quarantine_init); > -- > 2.18.0
On Mon, 2020-11-16 at 10:26 +0100, Dmitry Vyukov wrote: > On Mon, Nov 16, 2020 at 7:30 AM Kuan-Ying Lee > <Kuan-Ying.Lee@mediatek.com> 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. > > > > [ 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@mediatek.com> > > Suggested-by: Dmitry Vyukov <dvyukov@google.com> > > Reported-by: Guangye Yang <guangye.yang@mediatek.com> > > Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> > > Cc: Alexander Potapenko <glider@google.com> > > Cc: Andrew Morton <akpm@linux-foundation.org> > > Cc: Matthias Brugger <matthias.bgg@gmail.com> > > --- > > mm/kasan/quarantine.c | 35 +++++++++++++++++++++++++++++++++++ > > 1 file changed, 35 insertions(+) > > > > diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c > > index 4c5375810449..16e618ea805e 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; > > + } I think we need to make sure objects will not be put in per-cpu quarantine which is offline. > > qlist_put(q, &info->quarantine_link, cache->size); > > if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) { > > qlist_move_all(q, &temp); > > @@ -328,3 +335,31 @@ 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); > > + q->offline = true; > > + qlist_free_all(q, NULL); > > Looks much nicer now! > > What is the story with interrupts in these callbacks? > In the previous patch you mentioned that this CPU can still receive > interrupts for a brief period of time. If these interrupts also free > something, can't we corrupt the per-cpu quarantine? In quarantine_put > we protect it by disabling interrupts I think. > Here is a situation. After we freed all objects from the per-cpu quarantine which is going offline, the interrupts happened. These interrupts free something and put objects into this per-cpu quarantine. If we call kmem_cache_destroy() now, slub still detect objects remain in the per-cpu quarantine and report "Object remaining" error. Thus, we need to check q->offline in quarantine_put and make sure the offline per-cpu quarantine is not corrupted. > > > + 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 < 0) > > + pr_err("kasan offline cpu quarantine register failed [%d]\n", ret); > > + return ret; > > +} > > +late_initcall(kasan_cpu_offline_quarantine_init); > > -- > > 2.18.0
On Tue, Nov 17, 2020 at 7:46 AM Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com> wrote: > > On Mon, 2020-11-16 at 10:26 +0100, Dmitry Vyukov wrote: > > On Mon, Nov 16, 2020 at 7:30 AM Kuan-Ying Lee > > <Kuan-Ying.Lee@mediatek.com> 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. > > > > > > [ 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@mediatek.com> > > > Suggested-by: Dmitry Vyukov <dvyukov@google.com> > > > Reported-by: Guangye Yang <guangye.yang@mediatek.com> > > > Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> > > > Cc: Alexander Potapenko <glider@google.com> > > > Cc: Andrew Morton <akpm@linux-foundation.org> > > > Cc: Matthias Brugger <matthias.bgg@gmail.com> > > > --- > > > mm/kasan/quarantine.c | 35 +++++++++++++++++++++++++++++++++++ > > > 1 file changed, 35 insertions(+) > > > > > > diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c > > > index 4c5375810449..16e618ea805e 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; > > > + } > > I think we need to make sure objects will not be put in per-cpu > quarantine which is offline. > > > > qlist_put(q, &info->quarantine_link, cache->size); > > > if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) { > > > qlist_move_all(q, &temp); > > > @@ -328,3 +335,31 @@ 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); > > > + q->offline = true; > > > + qlist_free_all(q, NULL); > > > > Looks much nicer now! > > > > What is the story with interrupts in these callbacks? > > In the previous patch you mentioned that this CPU can still receive > > interrupts for a brief period of time. If these interrupts also free > > something, can't we corrupt the per-cpu quarantine? In quarantine_put > > we protect it by disabling interrupts I think. > > > > Here is a situation. > After we freed all objects from the per-cpu quarantine which is going > offline, the interrupts happened. These interrupts free something and > put objects into this per-cpu quarantine. If we call > kmem_cache_destroy() now, slub still detect objects remain in > the per-cpu quarantine and report "Object remaining" error. > > Thus, we need to check q->offline in quarantine_put and make sure > the offline per-cpu quarantine is not corrupted. If an interrupt can happen later, can't it happen right during our call to qlist_free_all and corrupt the per-cpu cache? Perhaps we need something like: // ... explain the subtleness ... WRITE_ONCE(q->offline, true); barrier(); qlist_free_all(q, NULL); ? > > > + 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 < 0) > > > + pr_err("kasan offline cpu quarantine register failed [%d]\n", ret); > > > + return ret; > > > +} > > > +late_initcall(kasan_cpu_offline_quarantine_init); > > > -- > > > 2.18.0
On Tue, 2020-11-17 at 08:13 +0100, Dmitry Vyukov wrote: > On Tue, Nov 17, 2020 at 7:46 AM Kuan-Ying Lee > <Kuan-Ying.Lee@mediatek.com> wrote: > > > > On Mon, 2020-11-16 at 10:26 +0100, Dmitry Vyukov wrote: > > > On Mon, Nov 16, 2020 at 7:30 AM Kuan-Ying Lee > > > <Kuan-Ying.Lee@mediatek.com> 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. > > > > > > > > [ 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@mediatek.com> > > > > Suggested-by: Dmitry Vyukov <dvyukov@google.com> > > > > Reported-by: Guangye Yang <guangye.yang@mediatek.com> > > > > Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> > > > > Cc: Alexander Potapenko <glider@google.com> > > > > Cc: Andrew Morton <akpm@linux-foundation.org> > > > > Cc: Matthias Brugger <matthias.bgg@gmail.com> > > > > --- > > > > mm/kasan/quarantine.c | 35 +++++++++++++++++++++++++++++++++++ > > > > 1 file changed, 35 insertions(+) > > > > > > > > diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c > > > > index 4c5375810449..16e618ea805e 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; > > > > + } > > > > I think we need to make sure objects will not be put in per-cpu > > quarantine which is offline. > > > > > > qlist_put(q, &info->quarantine_link, cache->size); > > > > if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) { > > > > qlist_move_all(q, &temp); > > > > @@ -328,3 +335,31 @@ 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); > > > > + q->offline = true; > > > > + qlist_free_all(q, NULL); > > > > > > Looks much nicer now! > > > > > > What is the story with interrupts in these callbacks? > > > In the previous patch you mentioned that this CPU can still receive > > > interrupts for a brief period of time. If these interrupts also free > > > something, can't we corrupt the per-cpu quarantine? In quarantine_put > > > we protect it by disabling interrupts I think. > > > > > > > Here is a situation. > > After we freed all objects from the per-cpu quarantine which is going > > offline, the interrupts happened. These interrupts free something and > > put objects into this per-cpu quarantine. If we call > > kmem_cache_destroy() now, slub still detect objects remain in > > the per-cpu quarantine and report "Object remaining" error. > > > > Thus, we need to check q->offline in quarantine_put and make sure > > the offline per-cpu quarantine is not corrupted. > > If an interrupt can happen later, can't it happen right during our > call to qlist_free_all and corrupt the per-cpu cache? > Perhaps we need something like: > > // ... explain the subtleness ... > WRITE_ONCE(q->offline, true); > barrier(); > qlist_free_all(q, NULL); > > ? Yes, we need to add barrier to ensure the ordering. I did not think about that before. Thanks for the reminder. I will fix in v3. > > > > > + 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 < 0) > > > > + pr_err("kasan offline cpu quarantine register failed [%d]\n", ret); > > > > + return ret; > > > > +} > > > > +late_initcall(kasan_cpu_offline_quarantine_init); > > > > -- > > > > 2.18.0
diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c index 4c5375810449..16e618ea805e 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 +335,31 @@ 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); + q->offline = true; + qlist_free_all(q, NULL); + 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 < 0) + pr_err("kasan offline cpu quarantine register failed [%d]\n", ret); + return ret; +} +late_initcall(kasan_cpu_offline_quarantine_init);
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@mediatek.com> Suggested-by: Dmitry Vyukov <dvyukov@google.com> Reported-by: Guangye Yang <guangye.yang@mediatek.com> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Alexander Potapenko <glider@google.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Matthias Brugger <matthias.bgg@gmail.com> --- mm/kasan/quarantine.c | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+)