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From: Amol Grover <frextrite@gmail.com>
To: Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
	James Morris <jamorris@linux.microsoft.com>,
	Thomas Gleixner <tglx@linutronix.de>Peter Zijlstra
	<peterz@infradead.org>, Jann Horn <jannh@google.com>,
	David Howells <dhowells@redhat.com>,
	Shakeel Butt <shakeelb@google.com>,
	"Eric W . Biederman" <ebiederm@xmission.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Paul Moore <paul@paul-moore.com>, Eric Paris <eparis@redhat.com>
Cc: linux-kernel-mentees@lists.linuxfoundation.org,
	linux-kernel@vger.kernel.org, linux-audit@redhat.com,
	Joel Fernandes <joel@joelfernandes.org>,
	Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>,
	"Paul E . McKenney" <paulmck@kernel.org>,
	Amol Grover <frextrite@gmail.com>
Subject: [PATCH 1/3] sched: Remove __rcu annotation from cred pointer
Date: Fri,  7 Feb 2020 23:35:03 +0530	[thread overview]
Message-ID: <20200207180504.4200-1-frextrite@gmail.com> (raw)

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@google.com>
Co-developed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Amol Grover <frextrite@gmail.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

WARNING: multiple messages have this Message-ID (diff)
From: Amol Grover <frextrite@gmail.com>
To: Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
	James Morris <jamorris@linux.microsoft.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Jann Horn <jannh@google.com>, David Howells <dhowells@redhat.com>,
	Shakeel Butt <shakeelb@google.com>,
	"Eric W . Biederman" <ebiederm@xmission.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Paul Moore <paul@paul-moore.com>,Eric Paris <eparis@redhat.com>
Cc: "Paul E . McKenney" <paulmck@kernel.org>,
	linux-kernel@vger.kernel.org,
	Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>,
	linux-audit@redhat.com, Joel Fernandes <joel@joelfernandes.org>,
	linux-kernel-mentees@lists.linuxfoundation.org
Subject: [Linux-kernel-mentees] [PATCH 1/3] sched: Remove __rcu annotation from cred pointer
Date: Fri,  7 Feb 2020 23:35:03 +0530	[thread overview]
Message-ID: <20200207180504.4200-1-frextrite@gmail.com> (raw)

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@google.com>
Co-developed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Amol Grover <frextrite@gmail.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

_______________________________________________
Linux-kernel-mentees mailing list
Linux-kernel-mentees@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees

WARNING: multiple messages have this Message-ID (diff)
From: Amol Grover <frextrite@gmail.com>
To: Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
	James Morris <jamorris@linux.microsoft.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Jann Horn <jannh@google.com>, David Howells <dhowells@redhat.com>,
	Shakeel Butt <shakeelb@google.com>,
	"Eric W . Biederman" <ebiederm@xmission.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Paul Moore <paul@paul-moore.com>, Eric Paris <eparis@redhat.com>
Cc: linux-kernel-mentees@lists.linuxfoundation.org,
	linux-kernel@vger.kernel.org, linux-audit@redhat.com,
	Joel Fernandes <joel@joelfernandes.org>,
	Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>,
	"Paul E . McKenney" <paulmck@kernel.org>,
	Amol Grover <frextrite@gmail.com>
Subject: [PATCH 1/3] sched: Remove __rcu annotation from cred pointer
Date: Fri,  7 Feb 2020 23:35:03 +0530	[thread overview]
Message-ID: <20200207180504.4200-1-frextrite@gmail.com> (raw)

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@google.com>
Co-developed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Amol Grover <frextrite@gmail.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


             reply	other threads:[~2020-02-07 18:05 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-07 18:05 Amol Grover [this message]
2020-02-07 18:05 ` [PATCH 1/3] sched: Remove __rcu annotation from cred pointer Amol Grover
2020-02-07 18:05 ` [Linux-kernel-mentees] " Amol Grover
2020-02-07 18:05 ` [PATCH 2/3] cred: Do not use RCU primitives to access " Amol Grover
2020-02-07 18:05   ` Amol Grover
2020-02-07 18:05   ` [Linux-kernel-mentees] " Amol Grover
2020-02-07 18:05 ` [PATCH 3/3] auditsc: Do not use RCU primitive to read from " Amol Grover
2020-02-07 18:05   ` Amol Grover
2020-02-07 18:05   ` [Linux-kernel-mentees] " Amol Grover
2020-02-11 15:19   ` Paul Moore
2020-02-11 15:19     ` Paul Moore
2020-02-11 15:19     ` [Linux-kernel-mentees] " Paul Moore
2020-02-13  8:11     ` Amol Grover
2020-02-13  8:11       ` Amol Grover
2020-02-13  8:11       ` [Linux-kernel-mentees] " Amol Grover

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