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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 2/3] cred: Do not use RCU primitives to access cred pointer
Date: Fri,  7 Feb 2020 23:35:04 +0530	[thread overview]
Message-ID: <20200207180504.4200-2-frextrite@gmail.com> (raw)
In-Reply-To: <20200207180504.4200-1-frextrite@gmail.com>

Since task_struct::cred can only be used task-synchronously,
and is not visible to other threads under RCU context,
we do not require RCU primitives to read/write to it and incur
heavy barriers.

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/cred.h | 5 ++---
 kernel/cred.c        | 6 +++---
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/include/linux/cred.h b/include/linux/cred.h
index 18639c069263..5973791e5fe4 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -291,11 +291,10 @@ static inline void put_cred(const struct cred *_cred)
 /**
  * current_cred - Access the current task's subjective credentials
  *
- * Access the subjective credentials of the current task.  RCU-safe,
- * since nobody else can modify it.
+ * Access the subjective credentials of the current task.
  */
 #define current_cred() \
-	rcu_dereference_protected(current->cred, 1)
+	(current->cred)
 
 /**
  * current_real_cred - Access the current task's objective credentials
diff --git a/kernel/cred.c b/kernel/cred.c
index 809a985b1793..3956c31d068d 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -485,7 +485,7 @@ int commit_creds(struct cred *new)
 	if (new->user != old->user)
 		atomic_inc(&new->user->processes);
 	rcu_assign_pointer(task->real_cred, new);
-	rcu_assign_pointer(task->cred, new);
+	task->cred = new;
 	if (new->user != old->user)
 		atomic_dec(&old->user->processes);
 	alter_cred_subscribers(old, -2);
@@ -562,7 +562,7 @@ const struct cred *override_creds(const struct cred *new)
 	 */
 	get_new_cred((struct cred *)new);
 	alter_cred_subscribers(new, 1);
-	rcu_assign_pointer(current->cred, new);
+	current->cred = new;
 	alter_cred_subscribers(old, -1);
 
 	kdebug("override_creds() = %p{%d,%d}", old,
@@ -590,7 +590,7 @@ void revert_creds(const struct cred *old)
 	validate_creds(old);
 	validate_creds(override);
 	alter_cred_subscribers(old, 1);
-	rcu_assign_pointer(current->cred, old);
+	current->cred = old;
 	alter_cred_subscribers(override, -1);
 	put_cred(override);
 }
-- 
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 2/3] cred: Do not use RCU primitives to access cred pointer
Date: Fri,  7 Feb 2020 23:35:04 +0530	[thread overview]
Message-ID: <20200207180504.4200-2-frextrite@gmail.com> (raw)
In-Reply-To: <20200207180504.4200-1-frextrite@gmail.com>

Since task_struct::cred can only be used task-synchronously,
and is not visible to other threads under RCU context,
we do not require RCU primitives to read/write to it and incur
heavy barriers.

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/cred.h | 5 ++---
 kernel/cred.c        | 6 +++---
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/include/linux/cred.h b/include/linux/cred.h
index 18639c069263..5973791e5fe4 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -291,11 +291,10 @@ static inline void put_cred(const struct cred *_cred)
 /**
  * current_cred - Access the current task's subjective credentials
  *
- * Access the subjective credentials of the current task.  RCU-safe,
- * since nobody else can modify it.
+ * Access the subjective credentials of the current task.
  */
 #define current_cred() \
-	rcu_dereference_protected(current->cred, 1)
+	(current->cred)
 
 /**
  * current_real_cred - Access the current task's objective credentials
diff --git a/kernel/cred.c b/kernel/cred.c
index 809a985b1793..3956c31d068d 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -485,7 +485,7 @@ int commit_creds(struct cred *new)
 	if (new->user != old->user)
 		atomic_inc(&new->user->processes);
 	rcu_assign_pointer(task->real_cred, new);
-	rcu_assign_pointer(task->cred, new);
+	task->cred = new;
 	if (new->user != old->user)
 		atomic_dec(&old->user->processes);
 	alter_cred_subscribers(old, -2);
@@ -562,7 +562,7 @@ const struct cred *override_creds(const struct cred *new)
 	 */
 	get_new_cred((struct cred *)new);
 	alter_cred_subscribers(new, 1);
-	rcu_assign_pointer(current->cred, new);
+	current->cred = new;
 	alter_cred_subscribers(old, -1);
 
 	kdebug("override_creds() = %p{%d,%d}", old,
@@ -590,7 +590,7 @@ void revert_creds(const struct cred *old)
 	validate_creds(old);
 	validate_creds(override);
 	alter_cred_subscribers(old, 1);
-	rcu_assign_pointer(current->cred, old);
+	current->cred = old;
 	alter_cred_subscribers(override, -1);
 	put_cred(override);
 }
-- 
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 2/3] cred: Do not use RCU primitives to access cred pointer
Date: Fri,  7 Feb 2020 23:35:04 +0530	[thread overview]
Message-ID: <20200207180504.4200-2-frextrite@gmail.com> (raw)
In-Reply-To: <20200207180504.4200-1-frextrite@gmail.com>

Since task_struct::cred can only be used task-synchronously,
and is not visible to other threads under RCU context,
we do not require RCU primitives to read/write to it and incur
heavy barriers.

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/cred.h | 5 ++---
 kernel/cred.c        | 6 +++---
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/include/linux/cred.h b/include/linux/cred.h
index 18639c069263..5973791e5fe4 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -291,11 +291,10 @@ static inline void put_cred(const struct cred *_cred)
 /**
  * current_cred - Access the current task's subjective credentials
  *
- * Access the subjective credentials of the current task.  RCU-safe,
- * since nobody else can modify it.
+ * Access the subjective credentials of the current task.
  */
 #define current_cred() \
-	rcu_dereference_protected(current->cred, 1)
+	(current->cred)
 
 /**
  * current_real_cred - Access the current task's objective credentials
diff --git a/kernel/cred.c b/kernel/cred.c
index 809a985b1793..3956c31d068d 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -485,7 +485,7 @@ int commit_creds(struct cred *new)
 	if (new->user != old->user)
 		atomic_inc(&new->user->processes);
 	rcu_assign_pointer(task->real_cred, new);
-	rcu_assign_pointer(task->cred, new);
+	task->cred = new;
 	if (new->user != old->user)
 		atomic_dec(&old->user->processes);
 	alter_cred_subscribers(old, -2);
@@ -562,7 +562,7 @@ const struct cred *override_creds(const struct cred *new)
 	 */
 	get_new_cred((struct cred *)new);
 	alter_cred_subscribers(new, 1);
-	rcu_assign_pointer(current->cred, new);
+	current->cred = new;
 	alter_cred_subscribers(old, -1);
 
 	kdebug("override_creds() = %p{%d,%d}", old,
@@ -590,7 +590,7 @@ void revert_creds(const struct cred *old)
 	validate_creds(old);
 	validate_creds(override);
 	alter_cred_subscribers(old, 1);
-	rcu_assign_pointer(current->cred, old);
+	current->cred = old;
 	alter_cred_subscribers(override, -1);
 	put_cred(override);
 }
-- 
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 [PATCH 1/3] sched: Remove __rcu annotation from cred pointer Amol Grover
2020-02-07 18:05 ` Amol Grover
2020-02-07 18:05 ` [Linux-kernel-mentees] " Amol Grover
2020-02-07 18:05 ` Amol Grover [this message]
2020-02-07 18:05   ` [PATCH 2/3] cred: Do not use RCU primitives to access " 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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