File 58821300-x86-segment-attribute-handling.patch of Package xen

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File 58821300-x86-segment-attribute-handling.patch of Package xen (Revision 6bbfc10fa0cd4906a4b565a5ad40b57f)

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# Commit 366ff5f1b3252f9069d5aedb2ffc2567bb0a37c9
# Date 2017-01-20 14:39:12 +0100
# Author Jan Beulich <jbeulich@suse.com>
# Committer Jan Beulich <jbeulich@suse.com>
x86: segment attribute handling adjustments

Null selector loads into SS (possible in 64-bit mode only, and only in
rings other than ring 3) must not alter SS.DPL. (This was found to be
an issue on KVM, and fixed in Linux commit 33ab91103b.)

Further arch_set_info_hvm_guest() didn't make sure that the ASSERT()s
in hvm_set_segment_register() wouldn't trigger: Add further checks, but
tolerate (adjust) clear accessed (CS, SS, DS, ES) and busy (TR) bits.

Finally the setting of the accessed bits for user segments was lost by
commit dd5c85e312 ("x86/hvm: Reposition the modification of raw segment
data from the VMCB/VMCS"), yet VMX requires them to be set for usable
segments. Add respective ASSERT()s (the only path not properly setting
them was arch_set_info_hvm_guest()).

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -1315,16 +1315,24 @@ static inline int check_segment(struct s
         return 0;
     }
 
-    if ( seg != x86_seg_tr && !reg->attr.fields.s )
+    if ( seg == x86_seg_tr )
     {
-        gprintk(XENLOG_ERR,
-                "System segment provided for a code or data segment\n");
-        return -EINVAL;
-    }
+        if ( reg->attr.fields.s )
+        {
+            gprintk(XENLOG_ERR, "Code or data segment provided for TR\n");
+            return -EINVAL;
+        }
 
-    if ( seg == x86_seg_tr && reg->attr.fields.s )
+        if ( reg->attr.fields.type != SYS_DESC_tss_busy )
+        {
+            gprintk(XENLOG_ERR, "Non-32-bit-TSS segment provided for TR\n");
+            return -EINVAL;
+        }
+    }
+    else if ( !reg->attr.fields.s )
     {
-        gprintk(XENLOG_ERR, "Code or data segment provided for TR\n");
+        gprintk(XENLOG_ERR,
+                "System segment provided for a code or data segment\n");
         return -EINVAL;
     }
 
@@ -1387,7 +1395,8 @@ int arch_set_info_hvm_guest(struct vcpu
 #define SEG(s, r) ({                                                        \
     s = (struct segment_register){ .base = (r)->s ## _base,                 \
                                    .limit = (r)->s ## _limit,               \
-                                   .attr.bytes = (r)->s ## _ar };           \
+                                   .attr.bytes = (r)->s ## _ar |            \
+                                       (x86_seg_##s != x86_seg_tr ? 1 : 2) }; \
     check_segment(&s, x86_seg_ ## s); })
 
         rc = SEG(cs, regs);
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -1360,6 +1360,11 @@ protmode_load_seg(
         }
         memset(sreg, 0, sizeof(*sreg));
         sreg->sel = sel;
+
+        /* Since CPL == SS.DPL, we need to put back DPL. */
+        if ( seg == x86_seg_ss )
+            sreg->attr.fields.dpl = sel;
+
         return X86EMUL_OKAY;
     }

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File 58821300-x86-segment-attribute-handling.patch of Package xen (Revision 6bbfc10fa0cd4906a4b565a5ad40b57f)

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