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From: Kees Cook <keescook@chromium.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Kees Cook" <keescook@chromium.org>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Christian Brauner" <christian.brauner@ubuntu.com>,
	"Anand K Mistry" <amistry@google.com>,
	"Kenta.Tada@sony.com" <Kenta.Tada@sony.com>,
	"Alexey Gladkov" <legion@kernel.org>,
	"Michael Weiß" <michael.weiss@aisec.fraunhofer.de>,
	"Jann Horn" <jannh@google.com>, "Michal Hocko" <mhocko@suse.com>,
	"Helge Deller" <deller@gmx.de>,
	linux-fsdevel@vger.kernel.org,
	"kernel test robot" <oliver.sang@intel.com>,
	"Vito Caputo" <vcaputo@pengaru.com>,
	"Ingo Molnar" <mingo@redhat.com>,
	"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>,
	"Daniel Bristot de Oliveira" <bristot@redhat.com>,
	"Qi Zheng" <zhengqi.arch@bytedance.com>,
	"Tobin C. Harding" <me@tobin.cc>,
	"Tycho Andersen" <tycho@tycho.pizza>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Borislav Petkov" <bp@alien8.de>,
	"H. Peter Anvin" <hpa@zytor.com>,
	"Mark Rutland" <mark.rutland@arm.com>,
	"Jens Axboe" <axboe@kernel.dk>,
	"Stefan Metzmacher" <metze@samba.org>,
	"Lai Jiangshan" <laijs@linux.alibaba.com>,
	"Andy Lutomirski" <luto@kernel.org>,
	"Dave Hansen" <dave.hansen@linux.intel.com>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	"Ohhoon Kwon" <ohoono.kwon@samsung.com>,
	"Kalesh Singh" <kaleshsingh@google.com>,
	"YiFei Zhu" <yifeifz2@illinois.edu>,
	"Josh Poimboeuf" <jpoimboe@redhat.com>,
	linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org,
	x86@kernel.org
Subject: [PATCH v2 3/6] proc: Use task_is_running() for wchan in /proc/$pid/stat
Date: Wed, 29 Sep 2021 15:02:15 -0700	[thread overview]
Message-ID: <20210929220218.691419-4-keescook@chromium.org> (raw)
In-Reply-To: <20210929220218.691419-1-keescook@chromium.org>

The implementations of get_wchan() can be expensive. The only information
imparted here is whether or not a process is currently blocked in the
scheduler (and even this doesn't need to be exact). Avoid doing the
heavy lifting of stack walking and just report that information by using
task_is_running().

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Anand K Mistry <amistry@google.com>
Cc: "Kenta.Tada@sony.com" <Kenta.Tada@sony.com>
Cc: Alexey Gladkov <legion@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Michael Weiß" <michael.weiss@aisec.fraunhofer.de>
Cc: Jann Horn <jannh@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Helge Deller <deller@gmx.de>
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 fs/proc/array.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 49be8c8ef555..77cf4187adec 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -541,7 +541,7 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
 	}
 
 	if (permitted && (!whole || num_threads < 2))
-		wchan = get_wchan(task);
+		wchan = !task_is_running(task);
 	if (!whole) {
 		min_flt = task->min_flt;
 		maj_flt = task->maj_flt;
@@ -606,10 +606,7 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
 	 *
 	 * This works with older implementations of procps as well.
 	 */
-	if (wchan)
-		seq_puts(m, " 1");
-	else
-		seq_puts(m, " 0");
+	seq_put_decimal_ull(m, " ", wchan);
 
 	seq_put_decimal_ull(m, " ", 0);
 	seq_put_decimal_ull(m, " ", 0);
-- 
2.30.2


  parent reply	other threads:[~2021-09-29 22:02 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-29 22:02 [PATCH v2 0/6] wchan: Fix ORC support and leaky fallback Kees Cook
2021-09-29 22:02 ` [PATCH v2 1/6] Revert "proc/wchan: use printk format instead of lookup_symbol_name()" Kees Cook
2021-09-29 22:02 ` [PATCH v2 2/6] sched: Add wrapper for get_wchan() to keep task blocked Kees Cook
2021-09-30  8:27   ` Peter Zijlstra
2021-09-30  8:28     ` Peter Zijlstra
2021-09-30  8:29       ` Peter Zijlstra
2021-09-29 22:02 ` Kees Cook [this message]
2021-09-29 22:02 ` [PATCH v2 4/6] proc: Only report /proc/$pid/wchan when process is blocked Kees Cook
2021-09-29 22:02 ` [PATCH v2 5/6] x86: Fix get_wchan() to support the ORC unwinder Kees Cook
2021-09-29 22:02 ` [PATCH v2 6/6] leaking_addresses: Always print a trailing newline Kees Cook
2021-09-30 14:37   ` Tycho Andersen
2021-09-30  1:01 ` [PATCH v2 0/6] wchan: Fix ORC support and leaky fallback Josh Poimboeuf
2021-09-30  8:40   ` Peter Zijlstra
2021-09-30 15:18     ` Kees Cook
2021-09-30 18:39       ` Peter Zijlstra

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