2021-07-19 06:04:04

by Xiyu Yang

Subject: [PATCH] iommu/amd: Convert from atomic_t to refcount_t on device_state->count

refcount_t type and corresponding API can protect refcounters from
accidental underflow and overflow and further use-after-free situations.

Signed-off-by: Xiyu Yang <[email protected]>
Signed-off-by: Xin Tan <[email protected]>
---
drivers/iommu/amd/iommu_v2.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/iommu/amd/iommu_v2.c b/drivers/iommu/amd/iommu_v2.c
index f8d4ad421e07..15d64f916fe5 100644
--- a/drivers/iommu/amd/iommu_v2.c
+++ b/drivers/iommu/amd/iommu_v2.c
@@ -6,6 +6,7 @@

#define pr_fmt(fmt) "AMD-Vi: " fmt

+#include <linux/refcount.h>
#include <linux/mmu_notifier.h>
#include <linux/amd-iommu.h>
#include <linux/mm_types.h>
@@ -51,7 +52,7 @@ struct pasid_state {
struct device_state {
struct list_head list;
u16 devid;
- atomic_t count;
+ refcount_t count;
struct pci_dev *pdev;
struct pasid_state **states;
struct iommu_domain *domain;
@@ -113,7 +114,7 @@ static struct device_state *get_device_state(u16 devid)
spin_lock_irqsave(&state_lock, flags);
dev_state = __get_device_state(devid);
if (dev_state != NULL)
- atomic_inc(&dev_state->count);
+ refcount_inc(&dev_state->count);
spin_unlock_irqrestore(&state_lock, flags);

return dev_state;
@@ -144,7 +145,7 @@ static void free_device_state(struct device_state *dev_state)

static void put_device_state(struct device_state *dev_state)
{
- if (atomic_dec_and_test(&dev_state->count))
+ if (refcount_dec_and_test(&dev_state->count))
wake_up(&dev_state->wq);
}

@@ -765,7 +766,7 @@ int amd_iommu_init_device(struct pci_dev *pdev, int pasids)
for (dev_state->pasid_levels = 0; (tmp - 1) & ~0x1ff; tmp >>= 9)
dev_state->pasid_levels += 1;

- atomic_set(&dev_state->count, 1);
+ refcount_set(&dev_state->count, 1);
dev_state->max_pasids = pasids;

ret = -ENOMEM;
@@ -856,7 +857,7 @@ void amd_iommu_free_device(struct pci_dev *pdev)
* Wait until the last reference is dropped before freeing
* the device state.
*/
- wait_event(dev_state->wq, !atomic_read(&dev_state->count));
+ wait_event(dev_state->wq, !refcount_read(&dev_state->count));
free_device_state(dev_state);
}
EXPORT_SYMBOL(amd_iommu_free_device);
--
2.7.4

2021-07-19 09:11:26

by Will Deacon

Subject: Re: [PATCH] iommu/amd: Convert from atomic_t to refcount_t on device_state->count

On Mon, Jul 19, 2021 at 02:00:37PM +0800, Xiyu Yang wrote:
> refcount_t type and corresponding API can protect refcounters from
> accidental underflow and overflow and further use-after-free situations.
>
> Signed-off-by: Xiyu Yang <[email protected]>
> Signed-off-by: Xin Tan <[email protected]>
> ---
> drivers/iommu/amd/iommu_v2.c | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)

Can pasid_state::count be converted similarly?

Will

2021-07-22 19:35:40

by Suthikulpanit, Suravee

Subject: Re: [PATCH] iommu/amd: Convert from atomic_t to refcount_t on device_state->count

On 7/19/2021 1:00 AM, Xiyu Yang wrote:
> refcount_t type and corresponding API can protect refcounters from
> accidental underflow and overflow and further use-after-free situations.
>
> Signed-off-by: Xiyu Yang <[email protected]>
> Signed-off-by: Xin Tan <[email protected]>
> ---
> drivers/iommu/amd/iommu_v2.c | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)

Thanks,

Reviewed-by: Suravee Suthikulpanit <[email protected]>