[Xen-devel] [PATCH 4/4] x86: check for canonical address before doing page walks

["Jan Beulich" <JBeulich@xxxxxxxx>]

... as there doesn't really exists any valid mapping for them.

Particularly in the case of do_page_walk() this also avoids returning
non-NULL for such invalid input.

Suggested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/x86_64/mm.c
+++ b/xen/arch/x86/x86_64/mm.c
@@ -73,7 +73,7 @@ void *do_page_walk(struct vcpu *v, unsig
     l2_pgentry_t l2e, *l2t;
     l1_pgentry_t l1e, *l1t;
 
-    if ( is_hvm_vcpu(v) )
+    if ( is_hvm_vcpu(v) || !is_canonical_address(addr) )
         return NULL;
 
     l4t = map_domain_page(mfn);
--- a/xen/arch/x86/x86_64/traps.c
+++ b/xen/arch/x86/x86_64/traps.c
@@ -170,6 +170,8 @@ void show_page_walk(unsigned long addr)
     l1_pgentry_t l1e, *l1t;
 
     printk("Pagetable walk from %016lx:\n", addr);
+    if ( !is_canonical_address(addr) )
+        return;
 
     l4t = map_domain_page(mfn);
     l4e = l4t[l4_table_offset(addr)];

Attachment: x86-page-walk-non-canonical.patch
Description: Text document

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