[Xen-devel] [PATCH 17/29] drivers, pci: convert hv_pci_dev.refs from atomic_t to refcount_t

[Elena Reshetova <elena.reshetova@xxxxxxxxx>]

refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.

Signed-off-by: Elena Reshetova <elena.reshetova@xxxxxxxxx>
Signed-off-by: Hans Liljestrand <ishkamiel@xxxxxxxxx>
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: David Windsor <dwindsor@xxxxxxxxx>
---
 drivers/pci/host/pci-hyperv.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
index cd114c6..870deed 100644
--- a/drivers/pci/host/pci-hyperv.c
+++ b/drivers/pci/host/pci-hyperv.c
@@ -56,6 +56,7 @@
 #include <asm/apic.h>
 #include <linux/msi.h>
 #include <linux/hyperv.h>
+#include <linux/refcount.h>
 #include <asm/mshyperv.h>
 
 /*
@@ -421,7 +422,7 @@ enum hv_pcidev_ref_reason {
 struct hv_pci_dev {
        /* List protected by pci_rescan_remove_lock */
        struct list_head list_entry;
-       atomic_t refs;
+       refcount_t refs;
        enum hv_pcichild_state state;
        struct pci_function_description desc;
        bool reported_missing;
@@ -1254,13 +1255,13 @@ static void q_resource_requirements(void *context, 
struct pci_response *resp,
 static void get_pcichild(struct hv_pci_dev *hpdev,
                            enum hv_pcidev_ref_reason reason)
 {
-       atomic_inc(&hpdev->refs);
+       refcount_inc(&hpdev->refs);
 }
 
 static void put_pcichild(struct hv_pci_dev *hpdev,
                            enum hv_pcidev_ref_reason reason)
 {
-       if (atomic_dec_and_test(&hpdev->refs))
+       if (refcount_dec_and_test(&hpdev->refs))
                kfree(hpdev);
 }
 
@@ -1314,7 +1315,7 @@ static struct hv_pci_dev *new_pcichild_device(struct 
hv_pcibus_device *hbus,
        wait_for_completion(&comp_pkt.host_event);
 
        hpdev->desc = *desc;
-       get_pcichild(hpdev, hv_pcidev_ref_initial);
+       refcount_set(&hpdev->refs, 1);
        get_pcichild(hpdev, hv_pcidev_ref_childlist);
        spin_lock_irqsave(&hbus->device_list_lock, flags);
        list_add_tail(&hpdev->list_entry, &hbus->children);
-- 
2.7.4


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