| Message ID | 1605162252-23886-2-git-send-email-Kuan-Ying.Lee@mediatek.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Fix objects remain in the offline per-cpu quarantine | expand |
On Thu, Nov 12, 2020 at 7:25 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> > --- > 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. > */ Hi Kuan-Ying, Thanks for fixing this. > static DEFINE_PER_CPU(struct qlist_head, cpu_quarantine); > +static DEFINE_PER_CPU(int, cpu_quarantine_offline); I think cpu_quarantine_offline is better be part of cpu_quarantine because it logically is and we already obtain a pointer to cpu_quarantine in quarantine_put, so it will also make the code a bit shorter. > /* 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); This looks like a convoluted way to call qlink_free. I think it will be better to call qlink_free directly here. And why do we need this? Because CPU shutdown code can still free some objects afterwards? > + local_irq_restore(flags); > + return; You add both if/else and early return, this looks like unnecessary code complication. It would be simpler with: if (*offline) { qlink_free(...); return; } ... all current per-cpu local ... > + } > 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); I assume this local_irq_save/restore is to prevent some warnings from this_cpu_ptr. But CPU online/offline callbacks should run without preemption already (preempting/rescheduling on other CPUs does not make sense for them, right?), so I would assume that is already at least preemption disabled or something. Is there this_cpu_ptr variant that won't produce warnings on its own in cpu online/offline callbacks? This whole function could be a 1-liner: this_cpu_ptr(&cpu_quarantine)->offline = true; So I am trying to understand if we could avoid all this unnecessary danse. > + 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); We just want to drop the whole per-cpu cache at once, right? I would assume there should be a simpler way to do this all at once, rather than doing this per-slab. > + 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 > > -- > 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+unsubscribe@googlegroups.com. > To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/1605162252-23886-2-git-send-email-Kuan-Ying.Lee%40mediatek.com.
On Thu, 2020-11-12 at 09:39 +0100, Dmitry Vyukov wrote: > On Thu, Nov 12, 2020 at 7:25 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> > > --- > > 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. > > */ > > Hi Kuan-Ying, > > Thanks for fixing this. > > > static DEFINE_PER_CPU(struct qlist_head, cpu_quarantine); > > +static DEFINE_PER_CPU(int, cpu_quarantine_offline); > > I think cpu_quarantine_offline is better be part of cpu_quarantine > because it logically is and we already obtain a pointer to > cpu_quarantine in quarantine_put, so it will also make the code a bit > shorter. > Ok. Got it. > > > /* 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); > > This looks like a convoluted way to call qlink_free. I think it will > be better to call qlink_free directly here. > > And why do we need this? Because CPU shutdown code can still free some > objects afterwards? > Yes, it is because IRQ can happen during CPU shutdown and free some objects into offline CPU quarantine. > > + local_irq_restore(flags); > > + return; > > You add both if/else and early return, this looks like unnecessary > code complication. It would be simpler with: > > if (*offline) { > qlink_free(...); > return; > } > ... all current per-cpu local ... > > Thank you for reminder. v2 Will do it. > > + } > > 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); > > I assume this local_irq_save/restore is to prevent some warnings from > this_cpu_ptr. > But CPU online/offline callbacks should run without preemption already > (preempting/rescheduling on other CPUs does not make sense for them, > right?), so I would assume that is already at least preemption > disabled or something. Is there this_cpu_ptr variant that won't > produce warnings on its own in cpu online/offline callbacks? > This whole function could be a 1-liner: > this_cpu_ptr(&cpu_quarantine)->offline = true; > So I am trying to understand if we could avoid all this unnecessary danse. > Yes, it's unnecessary. v2 will fix it. > > > + 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); > > We just want to drop the whole per-cpu cache at once, right? I would > assume there should be a simpler way to do this all at once, rather > than doing this per-slab. > Yes. Is removing objects in per-cpu quarantine directly better? struct qlist_head *q; q = this_cpu_ptr(&cpu_quaratine); 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) > > + pr_err("kasan offline cpu quarantine register failed [%d]\n", ret); > > + return ret; > > +} > > +late_initcall(kasan_cpu_offline_quarantine_init); > > -- > > 2.18.0 > > > > -- > > 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+unsubscribe@googlegroups.com. > > To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/1605162252-23886-2-git-send-email-Kuan-Ying.Lee%40mediatek.com.
On Fri, Nov 13, 2020 at 3:32 AM Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com> wrote: > > On Thu, 2020-11-12 at 09:39 +0100, Dmitry Vyukov wrote: > > On Thu, Nov 12, 2020 at 7:25 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> > > > --- > > > 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. > > > */ > > > > Hi Kuan-Ying, > > > > Thanks for fixing this. > > > > > static DEFINE_PER_CPU(struct qlist_head, cpu_quarantine); > > > +static DEFINE_PER_CPU(int, cpu_quarantine_offline); > > > > I think cpu_quarantine_offline is better be part of cpu_quarantine > > because it logically is and we already obtain a pointer to > > cpu_quarantine in quarantine_put, so it will also make the code a bit > > shorter. > > > > Ok. Got it. > > > > > > /* 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); > > > > This looks like a convoluted way to call qlink_free. I think it will > > be better to call qlink_free directly here. > > > > And why do we need this? Because CPU shutdown code can still free some > > objects afterwards? > > > > Yes, it is because IRQ can happen during CPU shutdown and free some > objects into offline CPU quarantine. > > > > + local_irq_restore(flags); > > > + return; > > > > You add both if/else and early return, this looks like unnecessary > > code complication. It would be simpler with: > > > > if (*offline) { > > qlink_free(...); > > return; > > } > > ... all current per-cpu local ... > > > > > > Thank you for reminder. v2 Will do it. > > > > + } > > > 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); > > > > I assume this local_irq_save/restore is to prevent some warnings from > > this_cpu_ptr. > > But CPU online/offline callbacks should run without preemption already > > (preempting/rescheduling on other CPUs does not make sense for them, > > right?), so I would assume that is already at least preemption > > disabled or something. Is there this_cpu_ptr variant that won't > > produce warnings on its own in cpu online/offline callbacks? > > This whole function could be a 1-liner: > > this_cpu_ptr(&cpu_quarantine)->offline = true; > > So I am trying to understand if we could avoid all this unnecessary danse. > > > > Yes, it's unnecessary. v2 will fix it. > > > > > > + 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); > > > > We just want to drop the whole per-cpu cache at once, right? I would > > assume there should be a simpler way to do this all at once, rather > > than doing this per-slab. > > > > Yes. > Is removing objects in per-cpu quarantine directly better? Yes, single qlist_free_all call looks much better than iteration over all slabs and removing in parts under the mutex. > struct qlist_head *q; > q = this_cpu_ptr(&cpu_quaratine); > 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) > > > + pr_err("kasan offline cpu quarantine register failed [%d]\n", ret); > > > + return ret; > > > +} > > > +late_initcall(kasan_cpu_offline_quarantine_init); > > > -- > > > 2.18.0 > > > > > > -- > > > 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+unsubscribe@googlegroups.com. > > > To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/1605162252-23886-2-git-send-email-Kuan-Ying.Lee%40mediatek.com. > > -- > 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+unsubscribe@googlegroups.com. > To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/1605234714.30076.18.camel%40mtksdccf07.
On Fri, 2020-11-13 at 08:03 +0100, Dmitry Vyukov wrote: > On Fri, Nov 13, 2020 at 3:32 AM Kuan-Ying Lee > <Kuan-Ying.Lee@mediatek.com> wrote: > > > > On Thu, 2020-11-12 at 09:39 +0100, Dmitry Vyukov wrote: > > > On Thu, Nov 12, 2020 at 7:25 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> > > > > --- > > > > 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. > > > > */ > > > > > > Hi Kuan-Ying, > > > > > > Thanks for fixing this. > > > > > > > static DEFINE_PER_CPU(struct qlist_head, cpu_quarantine); > > > > +static DEFINE_PER_CPU(int, cpu_quarantine_offline); > > > > > > I think cpu_quarantine_offline is better be part of cpu_quarantine > > > because it logically is and we already obtain a pointer to > > > cpu_quarantine in quarantine_put, so it will also make the code a bit > > > shorter. > > > > > > > Ok. Got it. > > > > > > > > > /* 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); > > > > > > This looks like a convoluted way to call qlink_free. I think it will > > > be better to call qlink_free directly here. > > > > > > And why do we need this? Because CPU shutdown code can still free some > > > objects afterwards? > > > > > > > Yes, it is because IRQ can happen during CPU shutdown and free some > > objects into offline CPU quarantine. > > > > > > + local_irq_restore(flags); > > > > + return; > > > > > > You add both if/else and early return, this looks like unnecessary > > > code complication. It would be simpler with: > > > > > > if (*offline) { > > > qlink_free(...); > > > return; > > > } > > > ... all current per-cpu local ... > > > > > > > > > > Thank you for reminder. v2 Will do it. > > > > > > + } > > > > 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); > > > > > > I assume this local_irq_save/restore is to prevent some warnings from > > > this_cpu_ptr. > > > But CPU online/offline callbacks should run without preemption already > > > (preempting/rescheduling on other CPUs does not make sense for them, > > > right?), so I would assume that is already at least preemption > > > disabled or something. Is there this_cpu_ptr variant that won't > > > produce warnings on its own in cpu online/offline callbacks? > > > This whole function could be a 1-liner: > > > this_cpu_ptr(&cpu_quarantine)->offline = true; > > > So I am trying to understand if we could avoid all this unnecessary danse. > > > > > > > Yes, it's unnecessary. v2 will fix it. > > > > > > > > > + 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); > > > > > > We just want to drop the whole per-cpu cache at once, right? I would > > > assume there should be a simpler way to do this all at once, rather > > > than doing this per-slab. > > > > > > > Yes. > > Is removing objects in per-cpu quarantine directly better? > > Yes, single qlist_free_all call looks much better than iteration over > all slabs and removing in parts under the mutex. > Hi Dmitry, Got it. Thanks for your review and reminder. I will fix them in v2. Kuan-Ying > > struct qlist_head *q; > > q = this_cpu_ptr(&cpu_quaratine); > > 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) > > > > + pr_err("kasan offline cpu quarantine register failed [%d]\n", ret); > > > > + return ret; > > > > +} > > > > +late_initcall(kasan_cpu_offline_quarantine_init); > > > > -- > > > > 2.18.0 > > > > > > > > -- > > > > 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+unsubscribe@googlegroups.com. > > > > To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/1605162252-23886-2-git-send-email-Kuan-Ying.Lee%40mediatek.com. > > > > -- > > 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+unsubscribe@googlegroups.com. > > To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/1605234714.30076.18.camel%40mtksdccf07.
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);
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> --- mm/kasan/quarantine.c | 59 +++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 57 insertions(+), 2 deletions(-)