From 343cad8c70585c4dba8afc75e1ec1b7610605ab2 Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Mon, 28 Oct 2013 12:00:36 +0100 Subject: [PATCH] x86: refine address validity checks before accessing page tables In commit 40d66baa ("x86: correct LDT checks") and d06a0d71 ("x86: add address validity check to guest_map_l1e()") I didn't really pay attention to the fact that these checks would better be done before the paging_mode_translate() ones, as there's also no equivalent check down the shadow code paths involved here (at least not up to the first use of the address), and such generic checks shouldn't really be done by particular backend functions anyway. Signed-off-by: Jan Beulich Acked-by: Tim Deegan --- xen/include/asm-x86/paging.h | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/xen/include/asm-x86/paging.h b/xen/include/asm-x86/paging.h index e957b2fe23..cd7ee3be66 100644 --- a/xen/include/asm-x86/paging.h +++ b/xen/include/asm-x86/paging.h @@ -356,12 +356,14 @@ guest_map_l1e(struct vcpu *v, unsigned long addr, unsigned long *gl1mfn) { l2_pgentry_t l2e; + if ( unlikely(!__addr_ok(addr)) ) + return NULL; + if ( unlikely(paging_mode_translate(v->domain)) ) return paging_get_hostmode(v)->guest_map_l1e(v, addr, gl1mfn); /* Find this l1e and its enclosing l1mfn in the linear map */ - if ( !__addr_ok(addr) || - __copy_from_user(&l2e, + if ( __copy_from_user(&l2e, &__linear_l2_table[l2_linear_offset(addr)], sizeof(l2_pgentry_t)) != 0 ) return NULL; @@ -382,16 +384,21 @@ guest_unmap_l1e(struct vcpu *v, void *p) /* Read the guest's l1e that maps this address. */ static inline void -guest_get_eff_l1e(struct vcpu *v, unsigned long addr, void *eff_l1e) +guest_get_eff_l1e(struct vcpu *v, unsigned long addr, l1_pgentry_t *eff_l1e) { + if ( unlikely(!__addr_ok(addr)) ) + { + *eff_l1e = l1e_empty(); + return; + } + if ( likely(!paging_mode_translate(v->domain)) ) { ASSERT(!paging_mode_external(v->domain)); - if ( !__addr_ok(addr) || - __copy_from_user(eff_l1e, + if ( __copy_from_user(eff_l1e, &__linear_l1_table[l1_linear_offset(addr)], sizeof(l1_pgentry_t)) != 0 ) - *(l1_pgentry_t *)eff_l1e = l1e_empty(); + *eff_l1e = l1e_empty(); return; } -- 2.30.2