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From: Wei Chen <Wei.Chen@arm.com>
Subject: arm: crash the guest when it traps on external abort

If we spot a data or prefetch abort bearing the ESR_EL2.EA bit set, we
know that this is an external abort, and that should crash the guest.

This is CVE-2016-9817, part of XSA-201.

Signed-off-by: Wei Chen <Wei.Chen@arm.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Steve Capper <steve.capper@arm.com>
Reviewed-by: Julien Grall <Julien.Grall@arm.com>

--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -2383,6 +2383,15 @@ static void do_trap_instr_abort_guest(struct cpu_user_regs *regs,
     int rc;
     register_t gva = READ_SYSREG(FAR_EL2);
 
+    /*
+     * If this bit has been set, it means that this instruction abort is caused
+     * by a guest external abort. Currently we crash the guest to protect the
+     * hypervisor. In future one can better handle this by injecting a virtual
+     * abort to the guest.
+     */
+    if ( hsr.iabt.eat )
+        domain_crash_synchronous();
+
     switch ( hsr.iabt.ifsc & 0x3f )
     {
     case FSC_FLT_PERM ... FSC_FLT_PERM + 3:
@@ -2437,6 +2446,15 @@ static void do_trap_data_abort_guest(struct cpu_user_regs *regs,
         return;
     }
 
+    /*
+     * If this bit has been set, it means that this data abort is caused
+     * by a guest external abort. Currently we crash the guest to protect the
+     * hypervisor. In future one can better handle this by injecting a virtual
+     * abort to the guest.
+     */
+    if ( dabt.eat )
+        domain_crash_synchronous();
+
     info.dabt = dabt;
 #ifdef CONFIG_ARM_32
     info.gva = READ_CP32(HDFAR);