powerpc/sysfs: Disable writing to PURR in guest mode
commit d1211af3049f4c9c1d8d4eb8f8098cc4f4f0d0c7 upstream.
arch/powerpc/kernel/sysfs.c exports PURR with write permission.
This may be valid for kernel in phyp mode. But writing to
the file in guest mode causes crash due to a priviledge violation
Signed-off-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
[Backported to 3.4: adjust context]
Signed-off-by: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c
index 8302af6..a191a72 100644
--- a/arch/powerpc/kernel/sysfs.c
+++ b/arch/powerpc/kernel/sysfs.c
@@ -17,6 +17,7 @@
#include <asm/machdep.h>
#include <asm/smp.h>
#include <asm/pmc.h>
+#include <asm/firmware.h>
#include "cacheinfo.h"
@@ -179,15 +180,25 @@
SYSFS_PMCSETUP(dscr, SPRN_DSCR);
SYSFS_PMCSETUP(pir, SPRN_PIR);
+/*
+ Lets only enable read for phyp resources and
+ enable write when needed with a separate function.
+ Lets be conservative and default to pseries.
+ */
static DEVICE_ATTR(mmcra, 0600, show_mmcra, store_mmcra);
static DEVICE_ATTR(spurr, 0600, show_spurr, NULL);
static DEVICE_ATTR(dscr, 0600, show_dscr, store_dscr);
-static DEVICE_ATTR(purr, 0600, show_purr, store_purr);
+static DEVICE_ATTR(purr, 0400, show_purr, store_purr);
static DEVICE_ATTR(pir, 0400, show_pir, NULL);
unsigned long dscr_default = 0;
EXPORT_SYMBOL(dscr_default);
+static void add_write_permission_dev_attr(struct device_attribute *attr)
+{
+ attr->attr.mode |= 0200;
+}
+
static ssize_t show_dscr_default(struct device *dev,
struct device_attribute *attr, char *buf)
{
@@ -394,8 +405,11 @@
if (cpu_has_feature(CPU_FTR_MMCRA))
device_create_file(s, &dev_attr_mmcra);
- if (cpu_has_feature(CPU_FTR_PURR))
+ if (cpu_has_feature(CPU_FTR_PURR)) {
+ if (!firmware_has_feature(FW_FEATURE_LPAR))
+ add_write_permission_dev_attr(&dev_attr_purr);
device_create_file(s, &dev_attr_purr);
+ }
if (cpu_has_feature(CPU_FTR_SPURR))
device_create_file(s, &dev_attr_spurr);