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Subject[PATCH 3/3] kernel: irq: use kmem_cache for allocating struct irqaction
Date
After enabling alignment checks in UBSan I've noticed several
reports like this:

UBSan: Undefined behaviour in kernel/irq/manage.c:1315:13
member access within misaligned address ffff88007c274558
for type 'struct irqaction' which requires 16 byte alignment

struct irqaction declared with ____cacheline_internodealigned_in_smp
attribute. However in some cases it allocated dynamically via kmalloc().
In general case kmalloc() guaranties only sizeof(void *) alignment.
We should use a separate slab cache to make struct irqaction
properly aligned on SMP configuration.

Note: UBSan reports says that 'struct irqaction' requires 16 byte alignment.
It's wrong, in my setup it should be 64 bytes. This looks like a gcc bug,
but it doesn't change the fact that irqaction is misaligned.

Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
---
kernel/irq/internals.h | 2 ++
kernel/irq/irqdesc.c | 1 +
kernel/irq/manage.c | 14 ++++++++------
3 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h
index 4332d76..95b61c5 100644
--- a/kernel/irq/internals.h
+++ b/kernel/irq/internals.h
@@ -7,6 +7,7 @@
*/
#include <linux/irqdesc.h>
#include <linux/kernel_stat.h>
+#include <linux/slab.h>

#ifdef CONFIG_SPARSE_IRQ
# define IRQ_BITMAP_BITS (NR_IRQS + 8196)
@@ -17,6 +18,7 @@
#define istate core_internal_state__do_not_mess_with_it

extern bool noirqdebug;
+extern struct kmem_cache *irqaction_cachep;

/*
* Bits used by threaded handlers:
diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index f22cb87..52c3e4f 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -222,6 +222,7 @@ int __init early_irq_init(void)
init_irq_default_affinity();

irq_desc_cachep = KMEM_CACHE(irq_desc, SLAB_PANIC);
+ irqaction_cachep = KMEM_CACHE(irqaction, SLAB_PANIC);

/* Let arch update nr_irqs and return the nr of preallocated irqs */
initcnt = arch_probe_nr_irqs();
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 0a9104b..7c69597 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -21,6 +21,8 @@

#include "internals.h"

+struct kmem_cache *irqaction_cachep;
+
#ifdef CONFIG_IRQ_FORCED_THREADING
__read_mostly bool force_irqthreads;

@@ -1409,7 +1411,7 @@ void free_irq(unsigned int irq, void *dev_id)
#endif

chip_bus_lock(desc);
- kfree(__free_irq(irq, dev_id));
+ kmem_cache_free(irqaction_cachep, __free_irq(irq, dev_id));
chip_bus_sync_unlock(desc);
}
EXPORT_SYMBOL(free_irq);
@@ -1487,7 +1489,7 @@ int request_threaded_irq(unsigned int irq, irq_handler_t handler,
handler = irq_default_primary_handler;
}

- action = kzalloc(sizeof(struct irqaction), GFP_KERNEL);
+ action = kmem_cache_zalloc(irqaction_cachep, GFP_KERNEL);
if (!action)
return -ENOMEM;

@@ -1502,7 +1504,7 @@ int request_threaded_irq(unsigned int irq, irq_handler_t handler,
chip_bus_sync_unlock(desc);

if (retval)
- kfree(action);
+ kmem_cache_free(irqaction_cachep, action);

#ifdef CONFIG_DEBUG_SHIRQ_FIXME
if (!retval && (irqflags & IRQF_SHARED)) {
@@ -1683,7 +1685,7 @@ void free_percpu_irq(unsigned int irq, void __percpu *dev_id)
return;

chip_bus_lock(desc);
- kfree(__free_percpu_irq(irq, dev_id));
+ kmem_cache_free(irqaction_cachep, __free_percpu_irq(irq, dev_id));
chip_bus_sync_unlock(desc);
}

@@ -1738,7 +1740,7 @@ int request_percpu_irq(unsigned int irq, irq_handler_t handler,
!irq_settings_is_per_cpu_devid(desc))
return -EINVAL;

- action = kzalloc(sizeof(struct irqaction), GFP_KERNEL);
+ action = kmem_cache_zalloc(irqaction_cachep, GFP_KERNEL);
if (!action)
return -ENOMEM;

@@ -1752,7 +1754,7 @@ int request_percpu_irq(unsigned int irq, irq_handler_t handler,
chip_bus_sync_unlock(desc);

if (retval)
- kfree(action);
+ kmem_cache_free(irqaction_cachep, action);

return retval;
}
--
2.1.3


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