xen-gntdev: prevent using UNMAP_NOTIFY_CLEAR_BYTE on read-only mappings
Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index 2c4cc94..2a4733c 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -294,7 +294,9 @@
if (pgno >= offset && pgno < offset + pages && use_ptemod) {
void __user *tmp;
tmp = map->vma->vm_start + map->notify.addr;
- copy_to_user(tmp, &err, 1);
+ err = copy_to_user(tmp, &err, 1);
+ if (err)
+ return err;
map->notify.flags &= ~UNMAP_NOTIFY_CLEAR_BYTE;
} else if (pgno >= offset && pgno < offset + pages) {
uint8_t *tmp = kmap(map->pages[pgno]);
@@ -599,6 +601,12 @@
goto unlock_out;
found:
+ if ((op.action & UNMAP_NOTIFY_CLEAR_BYTE) &&
+ (map->flags & GNTMAP_readonly)) {
+ rc = -EINVAL;
+ goto unlock_out;
+ }
+
map->notify.flags = op.action;
map->notify.addr = op.index - (map->index << PAGE_SHIFT);
map->notify.event = op.event_channel_port;