[PATCH v2 hurd] pci-arbiter: Fix long standing bug with PCI access

[Damien Zammit]

Proxied memory was not rounded up to page size, causing
error with vm_map'ing  the underlying memory.

WARNING: Assumes pci memory resources are at least page aligned.
If not, this will expose part of next resource to userspace.

---
 pci-arbiter/netfs_impl.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/pci-arbiter/netfs_impl.c b/pci-arbiter/netfs_impl.c
index 4bb5c97a..82e618a7 100644
--- a/pci-arbiter/netfs_impl.c
+++ b/pci-arbiter/netfs_impl.c
@@ -577,6 +577,7 @@ get_filemap_region (struct node *node, vm_prot_t prot)
   vm_prot_t max_prot;
   size_t reg_num;
   struct pci_mem_region *region;
+  size_t rounded_size;
 
   /* Get region info */
   reg_num =
@@ -592,12 +593,17 @@ get_filemap_region (struct node *node, vm_prot_t prot)
   if (err)
     goto error;
 
+  /* WARNING: this rounds up the proxied region to a whole page.
+   * This may be a security risk, but is the only way to provide access
+   * to the final page of the memory region */
+  rounded_size = round_page (region->size);
+
   /* Create a new memory object proxy with the required protection */
   max_prot = (VM_PROT_READ | VM_PROT_WRITE) & prot;
   err =
     vm_region_create_proxy (mach_task_self (),
                            (vm_address_t) node->nn->ln->region_maps[reg_num],
-                           max_prot, region->size, &proxy);
+                           max_prot, rounded_size, &proxy);
   if (err)
     goto error;
 
-- 
2.45.2