[xen master] gnttab: don't silently truncate GFNs in compat setup-table handling

[patchbot@xxxxxxx]

commit 1043dfb165cad25b83419b353abe91278b2b4745
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Mon Dec 5 13:44:50 2022 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Dec 5 13:44:50 2022 +0100

    gnttab: don't silently truncate GFNs in compat setup-table handling
    
    Returning back truncated frame numbers is unhelpful: Quite likely
    they're not owned by the domain (if it's PV), or we may misguide the
    guest into writing grant entries into a page that it actually uses for
    other purposes.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/common/compat/grant_table.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/xen/common/compat/grant_table.c b/xen/common/compat/grant_table.c
index 744f9b6e3d..f8177c84c0 100644
--- a/xen/common/compat/grant_table.c
+++ b/xen/common/compat/grant_table.c
@@ -176,7 +176,12 @@ int compat_grant_table_op(
                     { \
                         for ( i = 0; i < (_s_)->nr_frames; ++i ) \
                         { \
-                            unsigned int frame = (_s_)->frame_list.p[i]; \
+                            compat_pfn_t frame = (_s_)->frame_list.p[i]; \
+                            if ( frame != (_s_)->frame_list.p[i] ) \
+                            { \
+                                (_s_)->status = GNTST_address_too_big; \
+                                break; \
+                            } \
                             if ( __copy_to_compat_offset((_d_)->frame_list, \
                                                          i, &frame, 1) ) \
                             { \
--
generated by git-patchbot for /home/xen/git/xen.git#master