[xen staging] common: map_vcpu_info() cosmetics

[patchbot@xxxxxxx]

commit 7ee7a3749bcb5d39ced5a1ee3e8284b2bb9abc29
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Tue Apr 6 16:17:42 2021 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Apr 6 16:17:42 2021 +0200

    common: map_vcpu_info() cosmetics
    
    Use ENXIO instead of EINVAL to cover the two cases of the address not
    satisfying the requirements. This will make an issue here better stand
    out at the call site.
    
    Also add a missing compat-mode related size check: If the sizes
    differed, other code in the function would need changing. Accompany this
    by a change to the initial sizeof() expression, tying it to the type of
    the variable we're actually after (matching e.g. the alignof() added by
    XSA-327).
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Acked-by: Julien Grall <jgrall@xxxxxxxxxx>
---
 xen/common/domain.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/xen/common/domain.c b/xen/common/domain.c
index d85984638a..cdda0d1f29 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -1427,17 +1427,18 @@ int map_vcpu_info(struct vcpu *v, unsigned long gfn, 
unsigned offset)
     struct page_info *page;
     unsigned int align;
 
-    if ( offset > (PAGE_SIZE - sizeof(vcpu_info_t)) )
-        return -EINVAL;
+    if ( offset > (PAGE_SIZE - sizeof(*new_info)) )
+        return -ENXIO;
 
 #ifdef CONFIG_COMPAT
+    BUILD_BUG_ON(sizeof(*new_info) != sizeof(new_info->compat));
     if ( has_32bit_shinfo(d) )
         align = alignof(new_info->compat);
     else
 #endif
         align = alignof(*new_info);
     if ( offset & (align - 1) )
-        return -EINVAL;
+        return -ENXIO;
 
     if ( !mfn_eq(v->vcpu_info_mfn, INVALID_MFN) )
         return -EINVAL;
--
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