linux-kernel - [PATCH AUTOSEL 4.19 251/258] fs/proc/base.c: use ns_capable instead of capable for timerslack

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Message-Id: <20190128155924.51521-251-sashal@kernel.org>
Date:   Mon, 28 Jan 2019 10:59:17 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Benjamin Gordon <bmgordon@...gle.com>,
        John Stultz <john.stultz@...aro.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Kees Cook <keescook@...omium.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Oren Laadan <orenl@...lrox.com>,
        Ruchi Kandoi <kandoiruchi@...gle.com>,
        Rom Lemarchand <romlem@...roid.com>,
        Todd Kjos <tkjos@...gle.com>, Colin Cross <ccross@...roid.com>,
        Nick Kralevich <nnk@...gle.com>,
        Dmitry Shmidt <dimitrysh@...gle.com>,
        Elliott Hughes <enh@...gle.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sasha Levin <sashal@...nel.org>, linux-fsdevel@...r.kernel.org
Subject: [PATCH AUTOSEL 4.19 251/258] fs/proc/base.c: use ns_capable instead of capable for timerslack_ns

From: Benjamin Gordon <bmgordon@...gle.com>

[ Upstream commit 8da0b4f692c6d90b09c91f271517db746a22ff67 ]

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.

Link: http://lkml.kernel.org/r/20181030180012.232896-1-bmgordon@google.com
Signed-off-by: Benjamin Gordon <bmgordon@...gle.com>
Acked-by: "Eric W. Biederman" <ebiederm@...ssion.com>
Cc: John Stultz <john.stultz@...aro.org>
Cc: "Eric W. Biederman" <ebiederm@...ssion.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: "Serge E. Hallyn" <serge@...lyn.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Arjan van de Ven <arjan@...ux.intel.com>
Cc: Oren Laadan <orenl@...lrox.com>
Cc: Ruchi Kandoi <kandoiruchi@...gle.com>
Cc: Rom Lemarchand <romlem@...roid.com>
Cc: Todd Kjos <tkjos@...gle.com>
Cc: Colin Cross <ccross@...roid.com>
Cc: Nick Kralevich <nnk@...gle.com>
Cc: Dmitry Shmidt <dimitrysh@...gle.com>
Cc: Elliott Hughes <enh@...gle.com>
Cc: Alexey Dobriyan <adobriyan@...il.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/proc/base.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 7e9f07bf260d..5bdcf2159ff0 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2356,10 +2356,13 @@ static ssize_t timerslack_ns_write(struct file *file, const char __user *buf,
 		return -ESRCH;
 
 	if (p != current) {
-		if (!capable(CAP_SYS_NICE)) {
+		rcu_read_lock();
+		if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) {
+			rcu_read_unlock();
 			count = -EPERM;
 			goto out;
 		}
+		rcu_read_unlock();
 
 		err = security_task_setscheduler(p);
 		if (err) {
@@ -2392,11 +2395,14 @@ static int timerslack_ns_show(struct seq_file *m, void *v)
 		return -ESRCH;
 
 	if (p != current) {
-
-		if (!capable(CAP_SYS_NICE)) {
+		rcu_read_lock();
+		if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) {
+			rcu_read_unlock();
 			err = -EPERM;
 			goto out;
 		}
+		rcu_read_unlock();
+
 		err = security_task_getscheduler(p);
 		if (err)
 			goto out;
-- 
2.19.1