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Open Source and information security mailing list archives
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Date: Thu, 23 Sep 2021 19:13:06 -0700 From: Andrew Morton <akpm@...ux-foundation.org> To: Kees Cook <keescook@...omium.org> Cc: Thomas Gleixner <tglx@...utronix.de>, Josh Poimboeuf <jpoimboe@...hat.com>, Vito Caputo <vcaputo@...garu.com>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>, Jens Axboe <axboe@...nel.dk>, Mark Rutland <mark.rutland@....com>, Peter Zijlstra <peterz@...radead.org>, Stefan Metzmacher <metze@...ba.org>, Andy Lutomirski <luto@...nel.org>, Lai Jiangshan <laijs@...ux.alibaba.com>, Christian Brauner <christian.brauner@...ntu.com>, "Kenta.Tada@...y.com" <Kenta.Tada@...y.com>, Daniel Bristot de Oliveira <bristot@...hat.com>, Michael Weiß <michael.weiss@...ec.fraunhofer.de>, Anand K Mistry <amistry@...gle.com>, Alexey Gladkov <legion@...nel.org>, Michal Hocko <mhocko@...e.com>, Helge Deller <deller@....de>, Dave Hansen <dave.hansen@...ux.intel.com>, Andrea Righi <andrea.righi@...onical.com>, Ohhoon Kwon <ohoono.kwon@...sung.com>, Kalesh Singh <kaleshsingh@...gle.com>, YiFei Zhu <yifeifz2@...inois.edu>, "Eric W. Biederman" <ebiederm@...ssion.com>, linux-kernel@...r.kernel.org, x86@...nel.org, linux-fsdevel@...r.kernel.org, linux-hardening@...r.kernel.org Subject: Re: [PATCH] proc: Disable /proc/$pid/wchan On Thu, 23 Sep 2021 16:31:05 -0700 Kees Cook <keescook@...omium.org> wrote: > The /proc/$pid/wchan file has been broken by default on x86_64 for 4 > years now[1]. [1] is hard to decrypt. I think it would be better if this changelog were to describe the problem directly, completely and succinctly? > As this remains a potential leak of either kernel > addresses (when symbolization fails) or limited observation of kernel > function progress, just remove the contents for good. > > Unconditionally set the contents to "0" and also mark the wchan > field in /proc/$pid/stat with 0. > > This leaves kernel/sched/fair.c as the only user of get_wchan(). But > again, since this was broken for 4 years, was this profiling logic > actually doing anything useful? Agree that returning a hard-wired "0\n" is the way to go.
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