xen-gntdev: Avoid double-mapping memory
If an already-mapped area of the device was mapped into userspace a
second time, a hypercall was incorrectly made to remap the memory
again. Avoid the hypercall on later mmap calls, and fail the mmap call
if a writable mapping is attempted on a read-only range.
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 4687cd5..2c4cc94 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -258,6 +258,9 @@
phys_addr_t addr;
if (!use_ptemod) {
+ /* Note: it could already be mapped */
+ if (map->map_ops[0].handle)
+ return 0;
for (i = 0; i < map->count; i++) {
addr = (phys_addr_t)
pfn_to_kaddr(page_to_pfn(map->pages[i]));
@@ -668,9 +671,15 @@
if (use_ptemod)
map->vma = vma;
- map->flags = GNTMAP_host_map;
- if (!(vma->vm_flags & VM_WRITE))
- map->flags |= GNTMAP_readonly;
+ if (map->flags) {
+ if ((vma->vm_flags & VM_WRITE) &&
+ (map->flags & GNTMAP_readonly))
+ return -EINVAL;
+ } else {
+ map->flags = GNTMAP_host_map;
+ if (!(vma->vm_flags & VM_WRITE))
+ map->flags |= GNTMAP_readonly;
+ }
spin_unlock(&priv->lock);