diff options
Diffstat (limited to 'system/xen/xsa/xsa182-unstable.patch')
| -rw-r--r-- | system/xen/xsa/xsa182-unstable.patch | 102 |
1 files changed, 102 insertions, 0 deletions
diff --git a/system/xen/xsa/xsa182-unstable.patch b/system/xen/xsa/xsa182-unstable.patch new file mode 100644 index 0000000000..3e40e8a530 --- /dev/null +++ b/system/xen/xsa/xsa182-unstable.patch @@ -0,0 +1,102 @@ +From 00593655e231ed5ea20704120037026e33b83fbb Mon Sep 17 00:00:00 2001 +From: Andrew Cooper <andrew.cooper3@citrix.com> +Date: Mon, 11 Jul 2016 14:32:03 +0100 +Subject: [PATCH] x86/pv: Remove unsafe bits from the mod_l?_entry() fastpath + +All changes in writeability and cacheability must go through full +re-validation. + +Rework the logic as a whitelist, to make it clearer to follow. + +This is XSA-182 + +Reported-by: Jérémie Boutoille <jboutoille@ext.quarkslab.com> +Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> +Reviewed-by: Tim Deegan <tim@xen.org> +--- + xen/arch/x86/mm.c | 28 ++++++++++++++++------------ + xen/include/asm-x86/page.h | 1 + + 2 files changed, 17 insertions(+), 12 deletions(-) + +diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c +index dbcf6cb..56ca19f 100644 +--- a/xen/arch/x86/mm.c ++++ b/xen/arch/x86/mm.c +@@ -1852,6 +1852,14 @@ static inline int update_intpte(intpte_t *p, + _t ## e_get_intpte(_o), _t ## e_get_intpte(_n), \ + (_m), (_v), (_ad)) + ++/* ++ * PTE flags that a guest may change without re-validating the PTE. ++ * All other bits affect translation, caching, or Xen's safety. ++ */ ++#define FASTPATH_FLAG_WHITELIST \ ++ (_PAGE_NX_BIT | _PAGE_AVAIL_HIGH | _PAGE_AVAIL | _PAGE_GLOBAL | \ ++ _PAGE_DIRTY | _PAGE_ACCESSED | _PAGE_USER) ++ + /* Update the L1 entry at pl1e to new value nl1e. */ + static int mod_l1_entry(l1_pgentry_t *pl1e, l1_pgentry_t nl1e, + unsigned long gl1mfn, int preserve_ad, +@@ -1891,9 +1899,8 @@ static int mod_l1_entry(l1_pgentry_t *pl1e, l1_pgentry_t nl1e, + nl1e = l1e_from_pfn(page_to_mfn(page), l1e_get_flags(nl1e)); + } + +- /* Fast path for identical mapping, r/w, presence, and cachability. */ +- if ( !l1e_has_changed(ol1e, nl1e, +- PAGE_CACHE_ATTRS | _PAGE_RW | _PAGE_PRESENT) ) ++ /* Fast path for sufficiently-similar mappings. */ ++ if ( !l1e_has_changed(ol1e, nl1e, ~FASTPATH_FLAG_WHITELIST) ) + { + adjust_guest_l1e(nl1e, pt_dom); + rc = UPDATE_ENTRY(l1, pl1e, ol1e, nl1e, gl1mfn, pt_vcpu, +@@ -1970,11 +1977,8 @@ static int mod_l2_entry(l2_pgentry_t *pl2e, + return -EINVAL; + } + +- /* Fast path for identical mapping and presence. */ +- if ( !l2e_has_changed(ol2e, nl2e, +- unlikely(opt_allow_superpage) +- ? _PAGE_PSE | _PAGE_RW | _PAGE_PRESENT +- : _PAGE_PRESENT) ) ++ /* Fast path for sufficiently-similar mappings. */ ++ if ( !l2e_has_changed(ol2e, nl2e, ~FASTPATH_FLAG_WHITELIST) ) + { + adjust_guest_l2e(nl2e, d); + if ( UPDATE_ENTRY(l2, pl2e, ol2e, nl2e, pfn, vcpu, preserve_ad) ) +@@ -2039,8 +2043,8 @@ static int mod_l3_entry(l3_pgentry_t *pl3e, + return -EINVAL; + } + +- /* Fast path for identical mapping and presence. */ +- if ( !l3e_has_changed(ol3e, nl3e, _PAGE_PRESENT) ) ++ /* Fast path for sufficiently-similar mappings. */ ++ if ( !l3e_has_changed(ol3e, nl3e, ~FASTPATH_FLAG_WHITELIST) ) + { + adjust_guest_l3e(nl3e, d); + rc = UPDATE_ENTRY(l3, pl3e, ol3e, nl3e, pfn, vcpu, preserve_ad); +@@ -2103,8 +2107,8 @@ static int mod_l4_entry(l4_pgentry_t *pl4e, + return -EINVAL; + } + +- /* Fast path for identical mapping and presence. */ +- if ( !l4e_has_changed(ol4e, nl4e, _PAGE_PRESENT) ) ++ /* Fast path for sufficiently-similar mappings. */ ++ if ( !l4e_has_changed(ol4e, nl4e, ~FASTPATH_FLAG_WHITELIST) ) + { + adjust_guest_l4e(nl4e, d); + rc = UPDATE_ENTRY(l4, pl4e, ol4e, nl4e, pfn, vcpu, preserve_ad); +diff --git a/xen/include/asm-x86/page.h b/xen/include/asm-x86/page.h +index 224852a..4ae387f 100644 +--- a/xen/include/asm-x86/page.h ++++ b/xen/include/asm-x86/page.h +@@ -313,6 +313,7 @@ void efi_update_l4_pgtable(unsigned int l4idx, l4_pgentry_t); + #define _PAGE_AVAIL2 _AC(0x800,U) + #define _PAGE_AVAIL _AC(0xE00,U) + #define _PAGE_PSE_PAT _AC(0x1000,U) ++#define _PAGE_AVAIL_HIGH (_AC(0x7ff, U) << 12) + #define _PAGE_NX (cpu_has_nx ? _PAGE_NX_BIT : 0) + /* non-architectural flags */ + #define _PAGE_PAGED 0x2000U +-- +2.1.4 + |