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Date: Wed, 2 Jan 2013 17:57:12 -0500
From: Daniel De Graaf <dgdegra@...ho.nsa.gov>
To: viro@...IV.linux.org.uk, konrad.wilk@...cle.com
Cc: david.vrabel@...rix.com, stefano.stabellini@...citrix.com,
xen-devel@...ts.xensource.com, linux-kernel@...r.kernel.org,
Daniel De Graaf <dgdegra@...ho.nsa.gov>
Subject: [PATCH 2/3] xen/gntdev: correctly unmap unlinked maps in mmu notifier
If gntdev_ioctl_unmap_grant_ref is called on a range before unmapping
it, the entry is removed from priv->maps and the later call to
mn_invl_range_start won't find it to do the unmapping. Fix this by
creating another list of freeable maps that the mmu notifier can search
and use to unmap grants.
Signed-off-by: Daniel De Graaf <dgdegra@...ho.nsa.gov>
---
drivers/xen/gntdev.c | 92 +++++++++++++++++++++++++++++++++++-----------------
1 file changed, 63 insertions(+), 29 deletions(-)
diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index cca62cc..9be3e5e 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -56,10 +56,15 @@ MODULE_PARM_DESC(limit, "Maximum number of grants that may be mapped by "
static atomic_t pages_mapped = ATOMIC_INIT(0);
static int use_ptemod;
+#define populate_freeable_maps use_ptemod
struct gntdev_priv {
+ /* maps with visible offsets in the file descriptor */
struct list_head maps;
- /* lock protects maps from concurrent changes */
+ /* maps that are not visible; will be freed on munmap.
+ * Only populated if populate_freeable_maps == 1 */
+ struct list_head freeable_maps;
+ /* lock protects maps and freeable_maps */
spinlock_t lock;
struct mm_struct *mm;
struct mmu_notifier mn;
@@ -193,7 +198,7 @@ static struct grant_map *gntdev_find_map_index(struct gntdev_priv *priv,
return NULL;
}
-static void gntdev_put_map(struct grant_map *map)
+static void gntdev_put_map(struct gntdev_priv *priv, struct grant_map *map)
{
if (!map)
return;
@@ -208,6 +213,12 @@ static void gntdev_put_map(struct grant_map *map)
evtchn_put(map->notify.event);
}
+ if (populate_freeable_maps && priv) {
+ spin_lock(&priv->lock);
+ list_del(&map->next);
+ spin_unlock(&priv->lock);
+ }
+
if (map->pages && !use_ptemod)
unmap_grant_pages(map, 0, map->count);
gntdev_free_map(map);
@@ -376,11 +387,11 @@ static void gntdev_vma_open(struct vm_area_struct *vma)
static void gntdev_vma_close(struct vm_area_struct *vma)
{
struct grant_map *map = vma->vm_private_data;
+ struct file *file = vma->vm_file;
+ struct gntdev_priv *priv = file->private_data;
pr_debug("gntdev_vma_close %p\n", vma);
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
@@ -393,7 +404,7 @@ static void gntdev_vma_close(struct vm_area_struct *vma)
spin_unlock(&priv->lock);
}
vma->vm_private_data = NULL;
- gntdev_put_map(map);
+ gntdev_put_map(priv, map);
}
static struct vm_operations_struct gntdev_vmops = {
@@ -403,33 +414,43 @@ static struct vm_operations_struct gntdev_vmops = {
/* ------------------------------------------------------------------ */
+static void unmap_if_in_range(struct grant_map *map,
+ unsigned long start, unsigned long end)
+{
+ unsigned long mstart, mend;
+ int err;
+
+ if (!map->vma)
+ return;
+ if (map->vma->vm_start >= end)
+ return;
+ if (map->vma->vm_end <= start)
+ return;
+ mstart = max(start, map->vma->vm_start);
+ mend = min(end, map->vma->vm_end);
+ pr_debug("map %d+%d (%lx %lx), range %lx %lx, mrange %lx %lx\n",
+ map->index, map->count,
+ map->vma->vm_start, map->vma->vm_end,
+ start, end, mstart, mend);
+ err = unmap_grant_pages(map,
+ (mstart - map->vma->vm_start) >> PAGE_SHIFT,
+ (mend - mstart) >> PAGE_SHIFT);
+ WARN_ON(err);
+}
+
static void mn_invl_range_start(struct mmu_notifier *mn,
struct mm_struct *mm,
unsigned long start, unsigned long end)
{
struct gntdev_priv *priv = container_of(mn, struct gntdev_priv, mn);
struct grant_map *map;
- unsigned long mstart, mend;
- int err;
spin_lock(&priv->lock);
list_for_each_entry(map, &priv->maps, next) {
- if (!map->vma)
- continue;
- if (map->vma->vm_start >= end)
- continue;
- if (map->vma->vm_end <= start)
- continue;
- mstart = max(start, map->vma->vm_start);
- mend = min(end, map->vma->vm_end);
- pr_debug("map %d+%d (%lx %lx), range %lx %lx, mrange %lx %lx\n",
- map->index, map->count,
- map->vma->vm_start, map->vma->vm_end,
- start, end, mstart, mend);
- err = unmap_grant_pages(map,
- (mstart - map->vma->vm_start) >> PAGE_SHIFT,
- (mend - mstart) >> PAGE_SHIFT);
- WARN_ON(err);
+ unmap_if_in_range(map, start, end);
+ }
+ list_for_each_entry(map, &priv->freeable_maps, next) {
+ unmap_if_in_range(map, start, end);
}
spin_unlock(&priv->lock);
}
@@ -458,6 +479,15 @@ static void mn_release(struct mmu_notifier *mn,
err = unmap_grant_pages(map, /* offset */ 0, map->count);
WARN_ON(err);
}
+ list_for_each_entry(map, &priv->freeable_maps, next) {
+ if (!map->vma)
+ continue;
+ pr_debug("map %d+%d (%lx %lx)\n",
+ map->index, map->count,
+ map->vma->vm_start, map->vma->vm_end);
+ err = unmap_grant_pages(map, /* offset */ 0, map->count);
+ WARN_ON(err);
+ }
spin_unlock(&priv->lock);
}
@@ -479,6 +509,7 @@ static int gntdev_open(struct inode *inode, struct file *flip)
return -ENOMEM;
INIT_LIST_HEAD(&priv->maps);
+ INIT_LIST_HEAD(&priv->freeable_maps);
spin_lock_init(&priv->lock);
if (use_ptemod) {
@@ -513,8 +544,9 @@ static int gntdev_release(struct inode *inode, struct file *flip)
while (!list_empty(&priv->maps)) {
map = list_entry(priv->maps.next, struct grant_map, next);
list_del(&map->next);
- gntdev_put_map(map);
+ gntdev_put_map(NULL /* already removed */, map);
}
+ WARN_ON(!list_empty(&priv->freeable_maps));
if (use_ptemod)
mmu_notifier_unregister(&priv->mn, priv->mm);
@@ -542,14 +574,14 @@ static long gntdev_ioctl_map_grant_ref(struct gntdev_priv *priv,
if (unlikely(atomic_add_return(op.count, &pages_mapped) > limit)) {
pr_debug("can't map: over limit\n");
- gntdev_put_map(map);
+ gntdev_put_map(NULL, map);
return err;
}
if (copy_from_user(map->grants, &u->refs,
sizeof(map->grants[0]) * op.count) != 0) {
- gntdev_put_map(map);
- return err;
+ gntdev_put_map(NULL, map);
+ return -EFAULT;
}
spin_lock(&priv->lock);
@@ -578,11 +610,13 @@ static long gntdev_ioctl_unmap_grant_ref(struct gntdev_priv *priv,
map = gntdev_find_map_index(priv, op.index >> PAGE_SHIFT, op.count);
if (map) {
list_del(&map->next);
+ if (populate_freeable_maps)
+ list_add_tail(&map->next, &priv->freeable_maps);
err = 0;
}
spin_unlock(&priv->lock);
if (map)
- gntdev_put_map(map);
+ gntdev_put_map(priv, map);
return err;
}
@@ -797,7 +831,7 @@ out_unlock_put:
out_put_map:
if (use_ptemod)
map->vma = NULL;
- gntdev_put_map(map);
+ gntdev_put_map(priv, map);
return err;
}
--
1.7.11.7
--
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