[Xen-changelog] [xen stable-4.6] x86: segment attribute handling adjustments

[patchbot@xxxxxxx]

commit 5c38a2e73623ebc7f51b62a7bf5293e748d1b623
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Thu Feb 9 10:35:24 2017 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Feb 9 10:35:24 2017 +0100

    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.)
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    master commit: 366ff5f1b3252f9069d5aedb2ffc2567bb0a37c9
    master date: 2017-01-20 14:39:12 +0100
---
 xen/arch/x86/x86_emulate/x86_emulate.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c 
b/xen/arch/x86/x86_emulate/x86_emulate.c
index d821eec..ad26983d 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -1202,6 +1202,11 @@ 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;
     }
 
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.6

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