Commit 243082e0 authored by Daniel De Graaf's avatar Daniel De Graaf Committed by Konrad Rzeszutek Wilk
Browse files

xen/gntalloc: fix reference counts on multi-page mappings 



When a multi-page mapping of gntalloc is created, the reference counts
of all pages in the vma are incremented. However, the vma open/close
operations only adjusted the reference count of the first page in the
mapping, leaking the other pages. Store a struct in the vm_private_data
to track the original page count to properly free the pages when the
last reference to the vma is closed.

Reported-by: default avatarAnil Madhavapeddy <anil@recoil.org>
Signed-off-by: default avatarDaniel De Graaf <dgdegra@tycho.nsa.gov>
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent 0105d2b4

drivers/xen/gntalloc.c

+43 −13
Original line number Diff line number Diff line
@@ -99,6 +99,12 @@ struct gntalloc_file_private_data { 
	uint64_t index;

};



struct gntalloc_vma_private_data {

	struct gntalloc_gref *gref;

	int users;

	int count;

};



static void __del_gref(struct gntalloc_gref *gref);



static void do_cleanup(void)
@@ -451,25 +457,39 @@ static long gntalloc_ioctl(struct file *filp, unsigned int cmd, 


static void gntalloc_vma_open(struct vm_area_struct *vma)

{

	struct gntalloc_gref *gref = vma->vm_private_data;

	if (!gref)

	struct gntalloc_vma_private_data *priv = vma->vm_private_data;



	if (!priv)

		return;



	mutex_lock(&gref_mutex);

	gref->users++;

	priv->users++;

	mutex_unlock(&gref_mutex);

}



static void gntalloc_vma_close(struct vm_area_struct *vma)

{

	struct gntalloc_gref *gref = vma->vm_private_data;

	if (!gref)

	struct gntalloc_vma_private_data *priv = vma->vm_private_data;

	struct gntalloc_gref *gref, *next;

	int i;



	if (!priv)

		return;



	mutex_lock(&gref_mutex);

	priv->users--;

	if (priv->users == 0) {

		gref = priv->gref;

		for (i = 0; i < priv->count; i++) {

			gref->users--;

			next = list_entry(gref->next_gref.next,

					  struct gntalloc_gref, next_gref);

			if (gref->users == 0)

				__del_gref(gref);

			gref = next;

		}

		kfree(priv);

	}

	mutex_unlock(&gref_mutex);

}
@@ -481,19 +501,25 @@ static struct vm_operations_struct gntalloc_vmops = { 
static int gntalloc_mmap(struct file *filp, struct vm_area_struct *vma)

{

	struct gntalloc_file_private_data *priv = filp->private_data;

	struct gntalloc_vma_private_data *vm_priv;

	struct gntalloc_gref *gref;

	int count = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;

	int rv, i;



	pr_debug("%s: priv %p, page %lu+%d\n", __func__,

		       priv, vma->vm_pgoff, count);



	if (!(vma->vm_flags & VM_SHARED)) {

		printk(KERN_ERR "%s: Mapping must be shared.\n", __func__);

		return -EINVAL;

	}



	vm_priv = kmalloc(sizeof(*vm_priv), GFP_KERNEL);

	if (!vm_priv)

		return -ENOMEM;



	mutex_lock(&gref_mutex);



	pr_debug("%s: priv %p,%p, page %lu+%d\n", __func__,

		       priv, vm_priv, vma->vm_pgoff, count);



	gref = find_grefs(priv, vma->vm_pgoff << PAGE_SHIFT, count);

	if (gref == NULL) {

		rv = -ENOENT;
@@ -502,9 +528,13 @@ static int gntalloc_mmap(struct file *filp, struct vm_area_struct *vma) 
		goto out_unlock;

	}



	vma->vm_private_data = gref;

	vm_priv->gref = gref;

	vm_priv->users = 1;

	vm_priv->count = count;



	vma->vm_private_data = vm_priv;



	vma->vm_flags |= VM_RESERVED;

	vma->vm_flags |= VM_RESERVED | VM_DONTEXPAND;



	vma->vm_ops = &gntalloc_vmops;

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