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Re: [Xen-devel] [PATCH for-4.12] x86/svm: Fix handling of ICEBP intercepts
- To: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Fri, 1 Feb 2019 14:54:11 +0000
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- Cc: Juergen Gross <jgross@xxxxxxxx>, Wei Liu <wei.liu2@xxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxx>, Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxx>, Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, Brian Woods <brian.woods@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Delivery-date: Fri, 01 Feb 2019 14:54:18 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Openpgp: preference=signencrypt
On 01/02/2019 14:52, Tamas K Lengyel wrote:
> On Fri, Feb 1, 2019 at 7:49 AM Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> wrote:
>> 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 raise #GP for 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>
>> ---
>> CC: Jan Beulich <JBeulich@xxxxxxxx>
>> CC: Wei Liu <wei.liu2@xxxxxxxxxx>
>> CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
>> CC: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
>> CC: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
>> CC: Brian Woods <brian.woods@xxxxxxx>
>> CC: Juergen Gross <jgross@xxxxxxxx>
>> CC: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
>> CC: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>
>>
>> This wants backporting to Xen 4.11
>> ---
>> 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 2584b90..e21091c 100644
>> --- a/xen/arch/x86/hvm/svm/svm.c
>> +++ b/xen/arch/x86/hvm/svm/svm.c
>> @@ -2758,6 +2758,9 @@ 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 ( !instr_len )
> Should that have been inst_len instead of instr_len?
Bah - serves me right not to refresh my patch before sending it. Yes -
this is a typo.
~Andrew
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