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authorDaniel De Graaf <dgdegra@tycho.nsa.gov>2013-01-02 22:57:11 +0000
committerKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2013-01-15 16:01:06 -0500
commit2512f298cb9886e06938e761c9e924c8448d9ab8 (patch)
tree959938beb9ef789e72217844d159c95604817ac5 /drivers/xen
parent99beae6cb8f4dd5dab81a370b79c3b1085848d89 (diff)
xen/gntdev: fix unsafe vma access
In gntdev_ioctl_get_offset_for_vaddr, we need to hold mmap_sem while calling find_vma() to avoid potentially having the result freed out from under us. Similarly, the MMU notifier functions need to synchronize with gntdev_vma_close to avoid map->vma being freed during their iteration. Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov> Reported-by: Al Viro <viro@ZenIV.linux.org.uk> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Diffstat (limited to 'drivers/xen')
-rw-r--r--drivers/xen/gntdev.c29
1 files changed, 24 insertions, 5 deletions
diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index 2e22df2f7a3f..cca62cc8549b 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -378,7 +378,20 @@ static void gntdev_vma_close(struct vm_area_struct *vma)
struct grant_map *map = vma->vm_private_data;
pr_debug("gntdev_vma_close %p\n", vma);
- map->vma = NULL;
+ if (use_ptemod) {
+ struct file *file = vma->vm_file;
+ struct gntdev_priv *priv = file->private_data;
+ /* It is possible that an mmu notifier could be running
+ * concurrently, so take priv->lock to ensure that the vma won't
+ * vanishing during the unmap_grant_pages call, since we will
+ * spin here until that completes. Such a concurrent call will
+ * not do any unmapping, since that has been done prior to
+ * closing the vma, but it may still iterate the unmap_ops list.
+ */
+ spin_lock(&priv->lock);
+ map->vma = NULL;
+ spin_unlock(&priv->lock);
+ }
vma->vm_private_data = NULL;
gntdev_put_map(map);
}
@@ -579,25 +592,31 @@ static long gntdev_ioctl_get_offset_for_vaddr(struct gntdev_priv *priv,
struct ioctl_gntdev_get_offset_for_vaddr op;
struct vm_area_struct *vma;
struct grant_map *map;
+ int rv = -EINVAL;
if (copy_from_user(&op, u, sizeof(op)) != 0)
return -EFAULT;
pr_debug("priv %p, offset for vaddr %lx\n", priv, (unsigned long)op.vaddr);
+ down_read(&current->mm->mmap_sem);
vma = find_vma(current->mm, op.vaddr);
if (!vma || vma->vm_ops != &gntdev_vmops)
- return -EINVAL;
+ goto out_unlock;
map = vma->vm_private_data;
if (!map)
- return -EINVAL;
+ goto out_unlock;
op.offset = map->index << PAGE_SHIFT;
op.count = map->count;
+ rv = 0;
- if (copy_to_user(u, &op, sizeof(op)) != 0)
+ out_unlock:
+ up_read(&current->mm->mmap_sem);
+
+ if (rv == 0 && copy_to_user(u, &op, sizeof(op)) != 0)
return -EFAULT;
- return 0;
+ return rv;
}
static long gntdev_ioctl_notify(struct gntdev_priv *priv, void __user *u)