[Xen-devel] [RFC Patch v4 5/9] check if mfn is supported by IOCTL_PRIVCMD_MMAPBATCH before calling ioctl()

[Wen Congyang <wency@xxxxxxxxxxxxxx>]

If mfn is invalid, ioctl(fd, IOCTL_PRIVCMD_MMAPBATCH, ..) also returns 0,
and set error information in error bits(bits28-31). So if the user input
a large valid mfn, we cannot reliably distinguish between a large MFN and
an error. So we should check the input mfn before calling ioctl().
The user can input more than one mfn, and part of them are ~0UL. In this
case, the user expects we can map the memory for all valid mfn. So we
cannot just return NULL if some mfn is not supported.

Signed-off-by: Wen Congyang <wency@xxxxxxxxxxxxxx>
---
 tools/libxc/xc_linux_osdep.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/tools/libxc/xc_linux_osdep.c b/tools/libxc/xc_linux_osdep.c
index a19e4b6..d11bcee 100644
--- a/tools/libxc/xc_linux_osdep.c
+++ b/tools/libxc/xc_linux_osdep.c
@@ -321,6 +321,18 @@ static void *linux_privcmd_map_foreign_bulk(xc_interface 
*xch, xc_osdep_handle h
         }
 
         memcpy(pfn, arr, num * sizeof(*arr));
+        for ( i = 0; i < num; i++ )
+        {
+            /*
+             * IOCTL_PRIVCMD_MMAPBATCH doesn't support the mfn which
+             * error bits are set
+             */
+            if ( pfn[i] & PRIVCMD_MMAPBATCH_MFN_ERROR )
+            {
+                pfn[i] = ~0UL;
+                err[i] = -EINVAL;
+            }
+        }
 
         ioctlx.num = num;
         ioctlx.dom = dom;
@@ -333,6 +345,9 @@ static void *linux_privcmd_map_foreign_bulk(xc_interface 
*xch, xc_osdep_handle h
 
         for ( i = 0; i < num; ++i )
         {
+            if ( pfn[i] == ~0UL )
+                continue;
+
             switch ( pfn[i] ^ arr[i] )
             {
             case 0:
-- 
1.9.3


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel