[PATCH] proc: use ns_capable instead of capable for timerslack_ns

[bmgordon]

From: Benjamin Gordon <bmgordon@xxxxxxxxxx>

Access to timerslack_ns is controlled by a process having CAP_SYS_NICE
in its effective capability set, but the current check looks in the root
namespace instead of the process' user namespace.  Since a process is
allowed to do other activities controlled by CAP_SYS_NICE inside a
namespace, it should also be able to adjust timerslack_ns.

Signed-off-by: Benjamin Gordon <bmgordon@xxxxxxxxxx>
Cc: John Stultz <john.stultz@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: "Serge E. Hallyn" <serge@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
Cc: Oren Laadan <orenl@xxxxxxxxxxx>
Cc: Ruchi Kandoi <kandoiruchi@xxxxxxxxxx>
Cc: Rom Lemarchand <romlem@xxxxxxxxxxx>
Cc: Todd Kjos <tkjos@xxxxxxxxxx>
Cc: Colin Cross <ccross@xxxxxxxxxxx>
Cc: Nick Kralevich <nnk@xxxxxxxxxx>
Cc: Dmitry Shmidt <dimitrysh@xxxxxxxxxx>
Cc: Elliott Hughes <enh@xxxxxxxxxx>
Cc: Android Kernel Team <kernel-team@xxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
 fs/proc/base.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 7e9f07bf260d..4b50937dff80 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2356,7 +2356,7 @@ static ssize_t timerslack_ns_write(struct file *file, const char __user *buf,
 		return -ESRCH;
 
 	if (p != current) {
-		if (!capable(CAP_SYS_NICE)) {
+		if (!ns_capable(file->f_cred->user_ns, CAP_SYS_NICE)) {
 			count = -EPERM;
 			goto out;
 		}
@@ -2393,7 +2393,7 @@ static int timerslack_ns_show(struct seq_file *m, void *v)
 
 	if (p != current) {
 
-		if (!capable(CAP_SYS_NICE)) {
+		if (!ns_capable(seq_user_ns(m), CAP_SYS_NICE)) {
 			err = -EPERM;
 			goto out;
 		}
-- 
2.19.1.331.ge82ca0e54c-goog