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drivers, xen: convert grant_map.users from atomic_t to refcount_t 

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@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
This commit is contained in:
Elena Reshetova 2017-03-06 16:21:16 +02:00 committed by Boris Ostrovsky
parent 4495c08e84
commit c5f7c5a9a0
1 changed files with 6 additions and 5 deletions
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11
drivers/xen/gntdev.c
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@ -36,6 +36,7 @@
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/highmem.h>
#include <linux/refcount.h>
#include <xen/xen.h>
#include <xen/grant_table.h>
@ -86,7 +87,7 @@ struct grant_map {
int index;
int count;
int flags;
atomic_t users;
refcount_t users;
struct unmap_notify notify;
struct ioctl_gntdev_grant_ref *grants;
struct gnttab_map_grant_ref *map_ops;
@ -166,7 +167,7 @@ static struct grant_map *gntdev_alloc_map(struct gntdev_priv *priv, int count)
add->index = 0;
add->count = count;
atomic_set(&add->users, 1);
refcount_set(&add->users, 1);
return add;
@ -212,7 +213,7 @@ static void gntdev_put_map(struct gntdev_priv *priv, struct grant_map *map)
if (!map)
return;
if (!atomic_dec_and_test(&map->users))
if (!refcount_dec_and_test(&map->users))
return;
atomic_sub(map->count, &pages_mapped);
@ -400,7 +401,7 @@ static void gntdev_vma_open(struct vm_area_struct *vma)
struct grant_map *map = vma->vm_private_data;
pr_debug("gntdev_vma_open %p\n", vma);
atomic_inc(&map->users);
refcount_inc(&map->users);
}
static void gntdev_vma_close(struct vm_area_struct *vma)
@ -1004,7 +1005,7 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma)
goto unlock_out;
}
atomic_inc(&map->users);
refcount_inc(&map->users);
vma->vm_ops = &gntdev_vmops;