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powerpc/sysfs: Disable writing to PURR in guest mode

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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>
CC: <stable@vger.kernel.org>
This commit is contained in:
Madhavan Srinivasan 2013-10-02 00:34:10 +05:30 committed by Benjamin Herrenschmidt
parent 8f21bd0090
commit d1211af304
1 changed files with 16 additions and 2 deletions
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18
arch/powerpc/kernel/sysfs.c
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@ -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(spurr, SPRN_SPURR);
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, 0400, 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 @@ static void register_cpu_online(unsigned int cpu)
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);