Re: [PATCH v2 1/1] kasan: fix object remain in offline per-cpu quarantine
On Tue, 2020-11-17 at 08:13 +0100, Dmitry Vyukov wrote:
> On Tue, Nov 17, 2020 at 7:46 AM Kuan-Ying Lee
> 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
> > > 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=0x20010200
> > > > [ 74.986638] CPU: 3 PID: 176 Comm: cat Tainted: GB
> > > > 5.10.0-rc1-7-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
> > > > Suggested-by: Dmitry Vyukov
> > > > Reported-by: Guangye Yang
> > > > Cc: Andrey Ryabinin
> > > > Cc: Alexander Potapenko
> > > > Cc: Andrew Morton
> > > > Cc: Matthias Brugger
> > > > ---
> > > > 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
> > > > #include
> > > > #include
> > > > +#include
> > > >
> > > > #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(_quarantine);
> > > > + if (q->offline) {
> > > > + qlink_free(>quarantine_link, cache);
> > > > + local_irq_restore(flags);
> > > > + return;
> > > > + }
> >
> > I
Re: [PATCH v2 1/1] kasan: fix object remain in offline per-cpu quarantine
On Tue, Nov 17, 2020 at 7:46 AM Kuan-Ying Lee
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
> > 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=0x20010200
> > > [ 74.986638] CPU: 3 PID: 176 Comm: cat Tainted: GB
> > > 5.10.0-rc1-7-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
> > > Suggested-by: Dmitry Vyukov
> > > Reported-by: Guangye Yang
> > > Cc: Andrey Ryabinin
> > > Cc: Alexander Potapenko
> > > Cc: Andrew Morton
> > > Cc: Matthias Brugger
> > > ---
> > > 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
> > > #include
> > > #include
> > > +#include
> > >
> > > #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(_quarantine);
> > > + if (q->offline) {
> > > + qlink_free(>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, >quarantine_link, cache->size);
> > > if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) {
> > > qlist_move_all(q, );
> > > @@ -328,3 +335,31
Re: [PATCH v2 1/1] kasan: fix object remain in offline per-cpu quarantine
On Mon, 2020-11-16 at 10:26 +0100, Dmitry Vyukov wrote:
> On Mon, Nov 16, 2020 at 7:30 AM 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.
> >
> > [ 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=0x20010200
> > [ 74.986638] CPU: 3 PID: 176 Comm: cat Tainted: GB
> > 5.10.0-rc1-7-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
> > Suggested-by: Dmitry Vyukov
> > Reported-by: Guangye Yang
> > Cc: Andrey Ryabinin
> > Cc: Alexander Potapenko
> > Cc: Andrew Morton
> > Cc: Matthias Brugger
> > ---
> > 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
> > #include
> > #include
> > +#include
> >
> > #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(_quarantine);
> > + if (q->offline) {
> > + qlink_free(>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, >quarantine_link, cache->size);
> > if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) {
> > qlist_move_all(q, );
> > @@ -328,3 +335,31 @@ void quarantine_remove_cache(struct kmem_cache *cache)
> >
> > synchronize_srcu(_cache_srcu);
> > }
> > +
> > +static int kasan_cpu_online(unsigned int cpu)
> > +{
> > + this_cpu_ptr(_quarantine)->offline = false;
> > + return 0;
> > +}
> > +
> > +static int
Re: [PATCH v2 1/1] kasan: fix object remain in offline per-cpu quarantine
On Mon, Nov 16, 2020 at 7:30 AM 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.
>
> [ 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=0x20010200
> [ 74.986638] CPU: 3 PID: 176 Comm: cat Tainted: GB
> 5.10.0-rc1-7-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
> Suggested-by: Dmitry Vyukov
> Reported-by: Guangye Yang
> Cc: Andrey Ryabinin
> Cc: Alexander Potapenko
> Cc: Andrew Morton
> Cc: Matthias Brugger
> ---
> 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
> #include
> #include
> +#include
>
> #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(_quarantine);
> + if (q->offline) {
> + qlink_free(>quarantine_link, cache);
> + local_irq_restore(flags);
> + return;
> + }
> qlist_put(q, >quarantine_link, cache->size);
> if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) {
> qlist_move_all(q, );
> @@ -328,3 +335,31 @@ void quarantine_remove_cache(struct kmem_cache *cache)
>
> synchronize_srcu(_cache_srcu);
> }
> +
> +static int kasan_cpu_online(unsigned int cpu)
> +{
> + this_cpu_ptr(_quarantine)->offline = false;
> + return 0;
> +}
> +
> +static int kasan_cpu_offline(unsigned int cpu)
> +{
> + struct qlist_head *q;
> +
> + q = this_cpu_ptr(_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,
[PATCH v2 1/1] kasan: fix object remain in offline per-cpu quarantine
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=0x20010200
[ 74.986638] CPU: 3 PID: 176 Comm: cat Tainted: GB
5.10.0-rc1-7-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
Suggested-by: Dmitry Vyukov
Reported-by: Guangye Yang
Cc: Andrey Ryabinin
Cc: Alexander Potapenko
Cc: Andrew Morton
Cc: Matthias Brugger
---
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
#include
#include
+#include
#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(_quarantine);
+ if (q->offline) {
+ qlink_free(>quarantine_link, cache);
+ local_irq_restore(flags);
+ return;
+ }
qlist_put(q, >quarantine_link, cache->size);
if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) {
qlist_move_all(q, );
@@ -328,3 +335,31 @@ void quarantine_remove_cache(struct kmem_cache *cache)
synchronize_srcu(_cache_srcu);
}
+
+static int kasan_cpu_online(unsigned int cpu)
+{
+ this_cpu_ptr(_quarantine)->offline = false;
+ return 0;
+}
+
+static int kasan_cpu_offline(unsigned int cpu)
+{
+ struct qlist_head *q;
+
+ q = this_cpu_ptr(_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);
--
2.18.0
