From: Julien Grall <julien.grall@linaro.org>
Date: Thu, 25 Jul 2013 15:21:30 +0000 (+0100)
Subject: xen/arm: Don't emulate the MMIO access if the instruction syndrome is invalid
X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~6602
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=d2a167258b0b10567eb7abe3f34cf14660ed424e;p=xen.git

xen/arm: Don't emulate the MMIO access if the instruction syndrome is invalid

When the instruction syndrome is not valid, the transfer register is unknown.
If this register is used in the emulation code (it's the case for the VGIC),
Xen can retrieve wrong data.

For safety, consider invalid instruction syndrome as wrong memory access.

Signed-off-by: Julien Grall <julien.grall@linaro.org>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
---

diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index f2ffcb7ae5..29690396e3 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -1010,6 +1010,10 @@ static void do_trap_data_abort_guest(struct cpu_user_regs *regs,
     if ( rc == -EFAULT )
         goto bad_data_abort;
 
+    /* XXX: Decode the instruction if ISS is not valid */
+    if ( !dabt.valid )
+        goto bad_data_abort;
+
     if (handle_mmio(&info))
     {
         regs->pc += dabt.len ? 4 : 2;