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authorFrancesco Ruggeri <fruggeri@arista.com>2019-11-20 08:47:27 +0300
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2019-11-29 12:31:12 +0300
commit833a426cc471b6088011b3d67f1dc4e147614647 (patch)
tree3ee114c6786b4cb9e9e908c185d4ca42faea0fc9 /drivers/acpi/osl.c
parent6e9f879684b46331f51d0c76ebee981c788417db (diff)
downloadlinux-833a426cc471b6088011b3d67f1dc4e147614647.tar.xz
ACPI: OSL: only free map once in osl.c
acpi_os_map_cleanup checks map->refcount outside of acpi_ioremap_lock before freeing the map. This creates a race condition the can result in the map being freed more than once. A panic can be caused by running for ((i=0; i<10; i++)) do for ((j=0; j<100000; j++)) do cat /sys/firmware/acpi/tables/data/BERT >/dev/null done & done This patch makes sure that only the process that drops the reference to 0 does the freeing. Fixes: b7c1fadd6c2e ("ACPI: Do not use krefs under a mutex in osl.c") Signed-off-by: Francesco Ruggeri <fruggeri@arista.com> Reviewed-by: Dmitry Safonov <0x7f454c46@gmail.com> Cc: All applicable <stable@vger.kernel.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/acpi/osl.c')
-rw-r--r--drivers/acpi/osl.c28
1 files changed, 17 insertions, 11 deletions
diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index a2e844a8e9ed..41168c027a5a 100644
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -374,19 +374,21 @@ void *__ref acpi_os_map_memory(acpi_physical_address phys, acpi_size size)
}
EXPORT_SYMBOL_GPL(acpi_os_map_memory);
-static void acpi_os_drop_map_ref(struct acpi_ioremap *map)
+/* Must be called with mutex_lock(&acpi_ioremap_lock) */
+static unsigned long acpi_os_drop_map_ref(struct acpi_ioremap *map)
{
- if (!--map->refcount)
+ unsigned long refcount = --map->refcount;
+
+ if (!refcount)
list_del_rcu(&map->list);
+ return refcount;
}
static void acpi_os_map_cleanup(struct acpi_ioremap *map)
{
- if (!map->refcount) {
- synchronize_rcu_expedited();
- acpi_unmap(map->phys, map->virt);
- kfree(map);
- }
+ synchronize_rcu_expedited();
+ acpi_unmap(map->phys, map->virt);
+ kfree(map);
}
/**
@@ -406,6 +408,7 @@ static void acpi_os_map_cleanup(struct acpi_ioremap *map)
void __ref acpi_os_unmap_iomem(void __iomem *virt, acpi_size size)
{
struct acpi_ioremap *map;
+ unsigned long refcount;
if (!acpi_permanent_mmap) {
__acpi_unmap_table(virt, size);
@@ -419,10 +422,11 @@ void __ref acpi_os_unmap_iomem(void __iomem *virt, acpi_size size)
WARN(true, PREFIX "%s: bad address %p\n", __func__, virt);
return;
}
- acpi_os_drop_map_ref(map);
+ refcount = acpi_os_drop_map_ref(map);
mutex_unlock(&acpi_ioremap_lock);
- acpi_os_map_cleanup(map);
+ if (!refcount)
+ acpi_os_map_cleanup(map);
}
EXPORT_SYMBOL_GPL(acpi_os_unmap_iomem);
@@ -457,6 +461,7 @@ void acpi_os_unmap_generic_address(struct acpi_generic_address *gas)
{
u64 addr;
struct acpi_ioremap *map;
+ unsigned long refcount;
if (gas->space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY)
return;
@@ -472,10 +477,11 @@ void acpi_os_unmap_generic_address(struct acpi_generic_address *gas)
mutex_unlock(&acpi_ioremap_lock);
return;
}
- acpi_os_drop_map_ref(map);
+ refcount = acpi_os_drop_map_ref(map);
mutex_unlock(&acpi_ioremap_lock);
- acpi_os_map_cleanup(map);
+ if (!refcount)
+ acpi_os_map_cleanup(map);
}
EXPORT_SYMBOL(acpi_os_unmap_generic_address);