[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] [PATCH for-4.12] x86/svm: Fix handling of ICEBP intercepts



On 2/1/19 4:49 PM, Andrew Cooper 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 )
+                    break;
              }
rc = hvm_monitor_debug(regs->rip,


Reviewed-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>


Thanks,
Razvan

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel

 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.