[Xen-changelog] [xen stable-4.12] x86/svm: Fix handling of ICEBP intercepts

[patchbot@xxxxxxx]

commit 136d10fe4dbea6e7f07b62faacbdcce1baad1eb0
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Tue Jun 4 15:37:18 2019 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Jun 4 15:37:18 2019 +0200

    x86/svm: Fix handling of ICEBP intercepts
    
    c/s 9338a37d "x86/svm: implement debug events" added support for 
introspecting
    ICEBP debug exceptions, but didn't account for the fact that
    svm_get_insn_len() (previously __get_instruction_length) can fail and may
    already have raised #GP with the guest.
    
    If svm_get_insn_len() fails, return back to guest context rather than
    continuing and mistaking a trap-style VMExit for a fault-style one.
    
    Spotted by Coverity.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
    Acked-by: Brian Woods <brian.woods@xxxxxxx>
    master commit: 1495b4ff9b4af2b9c0f12cdb6491082cecf34f86
    master date: 2019-05-13 10:35:37 +0100
---
 xen/arch/x86/hvm/svm/svm.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index 23d72e81e3..ec9fb763af 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -2757,6 +2757,9 @@ void svm_vmexit_handler(struct cpu_user_regs *regs)
             {
                 trap_type = X86_EVENTTYPE_PRI_SW_EXCEPTION;
                 inst_len = svm_get_insn_len(v, INSTR_ICEBP);
+
+                if ( !inst_len )
+                    break;
             }
 
             rc = hvm_monitor_debug(regs->rip,
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.12

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