[PATCH v2] powerpc/papr_scm: Limit the readability of 'perf_stats' sysfs attribute

[Vaibhav Jain]

The newly introduced 'perf_stats' attribute uses the default access
mode of 0444 letting non-root users access performance stats of an
nvdimm and potentially force the kernel into issuing large number of
expensive HCALLs. Since the information exposed by this attribute
cannot be cached hence its better to ward of access to this attribute
from users who don't need to access these performance statistics.

Hence this patch updates access mode of 'perf_stats' attribute to
be only readable by root users.

Fixes: 2d02bf835e573 ('powerpc/papr_scm: Fetch nvdimm performance stats from PHYP')
Reported-by: Aneesh Kumar K.V <aneesh.kumar at linux.ibm.com>
Signed-off-by: Vaibhav Jain <vaibhav at linux.ibm.com>
---
Change-log:

v2:
* Instead of checking for perfmon_capable() inside show_perf_stats()
  set the attribute as DEVICE_ATTR_ADMIN_RO [ Aneesh ]
* Update patch description
---
 arch/powerpc/platforms/pseries/papr_scm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
index f439f0dfea7d1..a88a707a608aa 100644
--- a/arch/powerpc/platforms/pseries/papr_scm.c
+++ b/arch/powerpc/platforms/pseries/papr_scm.c
@@ -822,7 +822,7 @@ static ssize_t perf_stats_show(struct device *dev,
 	kfree(stats);
 	return rc ? rc : seq_buf_used(&s);
 }
-DEVICE_ATTR_RO(perf_stats);
+DEVICE_ATTR_ADMIN_RO(perf_stats);
 
 static ssize_t flags_show(struct device *dev,
 			  struct device_attribute *attr, char *buf)
-- 
2.26.2