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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id u6sm582368pgr.3.2021.09.29.15.02.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 29 Sep 2021 15:02:20 -0700 (PDT) From: Kees Cook To: Peter Zijlstra Cc: Kees Cook , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , kernel test robot , Vito Caputo , Jann Horn , Andrew Morton , Christian Brauner , Anand K Mistry , "Kenta.Tada@sony.com" , Alexey Gladkov , =?UTF-8?q?Michael=20Wei=C3=9F?= , Michal Hocko , Helge Deller , Qi Zheng , "Tobin C. Harding" , Tycho Andersen , Thomas Gleixner , Borislav Petkov , "H. Peter Anvin" , Mark Rutland , Jens Axboe , Stefan Metzmacher , Lai Jiangshan , Andy Lutomirski , Dave Hansen , "Eric W. Biederman" , Ohhoon Kwon , Kalesh Singh , YiFei Zhu , Josh Poimboeuf , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-hardening@vger.kernel.org, x86@kernel.org Subject: [PATCH v2 2/6] sched: Add wrapper for get_wchan() to keep task blocked Date: Wed, 29 Sep 2021 15:02:14 -0700 Message-Id: <20210929220218.691419-3-keescook@chromium.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210929220218.691419-1-keescook@chromium.org> References: <20210929220218.691419-1-keescook@chromium.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2019; h=from:subject; bh=hDSVcS+yS4zZDdIDUOZIhgW3NO0PbtwfKyydbAUGaMU=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBhVOJoXE4lnUJcVhzfp3ihdwxyB+SepKuT2zcL6CCW aOKOM4iJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCYVTiaAAKCRCJcvTf3G3AJtD4EA CKIae2l/Y4dicmSYuz6SdCtnqA0Rd5XecPN40jZIiItJs97tI0zHJfZJ0grAuBL62iw0oTrDAep0rJ hbKWV0M7J6ZcSqjI/alre0T7Jp1q8rOp/PnsXrdt23dO2vZXQh/6qvDemzNIvxOpQ4xk1cEann4FyQ mb1o02iC6K5JJaKT7HJXFfQo3fi++ezzGECuBqyyZYFcIMx5RuTUS+ZpWNgraW+WZpPgzl6ZXGP4bn xB+1NZDZqY5Q9oZ8vuDm1SC/+QwmZJCrgyeQTS213hV7Kuv0qIo/GTM+v/+/jTbqfXPZUWNKUbB28I TxAnDGXvT77m6f1R0ihCffDBj36GLZF6X+u1Mb8BeSeg7UGxXLf9EdwMsZIGs9PhUL6titRBgNwAc0 R7vAin9+bCS4p/0Tl9HfHtJoIRUWleimK8KDxGOz6LuA8ZozXBRcwUuCoTwT+9nF4T06Nou/8fcvfF BSG0SkCgkr0ug2ebMP2txQ8gxIXcWKntvutRuw0xuKNeHWIGtg8JMccsidYwQ6l2D0q6FMDcE+K1QJ YU4/m+ZEpM1mrWDvBfI0i2fkC85s++MH3kuyyx15f8J6ZosClV6STeF5l8QBbZC5wWgoxEdV50MX+A QOOb4MBGs24mNWLO/oiPqGS21M141Fn88kp6/GifGhov5UAVvVKoaTEUseeA== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org Having a stable wchan means the process must be blocked and for it to stay that way while performing stack unwinding. Cc: Ingo Molnar Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Steven Rostedt Cc: Ben Segall Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Suggested-by: Peter Zijlstra Signed-off-by: Kees Cook --- include/linux/sched.h | 1 + kernel/sched/core.c | 16 ++++++++++++++++ 2 files changed, 17 insertions(+) diff --git a/include/linux/sched.h b/include/linux/sched.h index 39039ce8ac4c..0c8185089e20 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2137,6 +2137,7 @@ static inline void set_task_cpu(struct task_struct *p, unsigned int cpu) #endif /* CONFIG_SMP */ extern bool sched_task_on_rq(struct task_struct *p); +extern unsigned long sched_task_get_wchan(struct task_struct *p); /* * In order to reduce various lock holder preemption latencies provide an diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 1bba4128a3e6..4a30455e1ff5 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1962,6 +1962,22 @@ bool sched_task_on_rq(struct task_struct *p) return task_on_rq_queued(p); } +unsigned long sched_task_get_wchan(struct task_struct *p) +{ + unsigned int state; + unsigned long ip = 0; + + /* Only get wchan if task is blocked and we can keep it that way. */ + raw_spin_lock_irq(&p->pi_lock); + state = READ_ONCE(p->__state); + smp_rmb(); /* see try_to_wake_up() */ + if (state != TASK_RUNNING && state != TASK_WAKING && !p->on_rq) + ip = get_wchan(p); + raw_spin_unlock_irq(&p->pi_lock); + + return ip; +} + static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags) { if (!(flags & ENQUEUE_NOCLOCK)) -- 2.30.2