Merge tag 'linux-kselftest-4.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel...

[karo-tx-linux.git] / arch / arm / xen / hypercall.S

diff --git a/arch/arm/xen/hypercall.S b/arch/arm/xen/hypercall.S
index f00e080759384afd300398be488c5740f55f1091..10fd99c568c62a9296b4ad7d2cc3584360b1b8a0 100644 (file)
--- a/arch/arm/xen/hypercall.S
+++ b/arch/arm/xen/hypercall.S
@@ -98,8 +98,23 @@ ENTRY(privcmd_call)
        mov r1, r2
        mov r2, r3
        ldr r3, [sp, #8]
+       /*
+        * Privcmd calls are issued by the userspace. We need to allow the
+        * kernel to access the userspace memory before issuing the hypercall.
+        */
+       uaccess_enable r4
+
+       /* r4 is loaded now as we use it as scratch register before */
        ldr r4, [sp, #4]
        __HVC(XEN_IMM)
+
+       /*
+        * Disable userspace access from kernel. This is fine to do it
+        * unconditionally as no set_fs(KERNEL_DS)/set_fs(get_ds()) is
+        * called before.
+        */
+       uaccess_disable r4
+
        ldm sp!, {r4}
        ret lr
 ENDPROC(privcmd_call);