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Message-Id: <20200402055640.6677-1-frextrite@gmail.com>
Date: Thu, 2 Apr 2020 11:26:38 +0530
From: Amol Grover <frextrite@...il.com>
To: Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Juri Lelli <juri.lelli@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Steven Rostedt <rostedt@...dmis.org>,
Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
James Morris <jamorris@...ux.microsoft.com>,
Thomas Gleixner <tglx@...utronix.de>,
Peter Zijlstra <peterz@...radead.org>,
Jann Horn <jannh@...gle.com>,
David Howells <dhowells@...hat.com>,
Shakeel Butt <shakeelb@...gle.com>,
"Eric W . Biederman" <ebiederm@...ssion.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Paul Moore <paul@...l-moore.com>,
Eric Paris <eparis@...hat.com>
Cc: linux-kernel-mentees@...ts.linuxfoundation.org,
linux-kernel@...r.kernel.org, linux-audit@...hat.com,
Joel Fernandes <joel@...lfernandes.org>,
Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>,
"Paul E . McKenney" <paulmck@...nel.org>,
Amol Grover <frextrite@...il.com>
Subject: [PATCH 1/3 RESEND] sched: Remove __rcu annotation from cred pointer
task_struct::cred (subjective credentials) is *always* used
task-synchronously, hence, does not require RCU semantics.
task_struct::real_cred (objective credentials) can be used in
RCU context and its __rcu annotation is retained.
However, task_struct::cred and task_struct::real_cred *may*
point to the same object, hence, the object pointed to by
task_struct::cred *may* have RCU delayed freeing.
Suggested-by: Jann Horn <jannh@...gle.com>
Co-developed-by: Joel Fernandes (Google) <joel@...lfernandes.org>
Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
Signed-off-by: Amol Grover <frextrite@...il.com>
---
include/linux/sched.h | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 716ad1d8d95e..39924e6e0cf2 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -879,8 +879,11 @@ struct task_struct {
/* Objective and real subjective task credentials (COW): */
const struct cred __rcu *real_cred;
- /* Effective (overridable) subjective task credentials (COW): */
- const struct cred __rcu *cred;
+ /*
+ * Effective (overridable) subjective task credentials (COW)
+ * which is used task-synchronously
+ */
+ const struct cred *cred;
#ifdef CONFIG_KEYS
/* Cached requested key. */
--
2.24.1
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