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Date: Wed, 29 Sep 2021 15:02:13 -0700 From: Kees Cook <keescook@...omium.org> To: Peter Zijlstra <peterz@...radead.org> Cc: Kees Cook <keescook@...omium.org>, kernel test robot <oliver.sang@...el.com>, Vito Caputo <vcaputo@...garu.com>, Jann Horn <jannh@...gle.com>, stable@...r.kernel.org, Ingo Molnar <mingo@...hat.com>, Juri Lelli <juri.lelli@...hat.com>, Vincent Guittot <vincent.guittot@...aro.org>, Dietmar Eggemann <dietmar.eggemann@....com>, Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>, Daniel Bristot de Oliveira <bristot@...hat.com>, Andrew Morton <akpm@...ux-foundation.org>, Christian Brauner <christian.brauner@...ntu.com>, Anand K Mistry <amistry@...gle.com>, "Kenta.Tada@...y.com" <Kenta.Tada@...y.com>, Alexey Gladkov <legion@...nel.org>, Michael Weiß <michael.weiss@...ec.fraunhofer.de>, Michal Hocko <mhocko@...e.com>, Helge Deller <deller@....de>, Qi Zheng <zhengqi.arch@...edance.com>, "Tobin C. Harding" <me@...in.cc>, Tycho Andersen <tycho@...ho.pizza>, Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>, Mark Rutland <mark.rutland@....com>, Jens Axboe <axboe@...nel.dk>, Stefan Metzmacher <metze@...ba.org>, Lai Jiangshan <laijs@...ux.alibaba.com>, Andy Lutomirski <luto@...nel.org>, Dave Hansen <dave.hansen@...ux.intel.com>, "Eric W. Biederman" <ebiederm@...ssion.com>, Ohhoon Kwon <ohoono.kwon@...sung.com>, Kalesh Singh <kaleshsingh@...gle.com>, YiFei Zhu <yifeifz2@...inois.edu>, Josh Poimboeuf <jpoimboe@...hat.com>, linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org, linux-hardening@...r.kernel.org, x86@...nel.org Subject: [PATCH v2 1/6] Revert "proc/wchan: use printk format instead of lookup_symbol_name()" This reverts commit 152c432b128cb043fc107e8f211195fe94b2159c. When a kernel address couldn't be symbolized for /proc/$pid/wchan, it would leak the raw value, a potential information exposure. This is a regression compared to the safer pre-v5.12 behavior. Reported-by: kernel test robot <oliver.sang@...el.com> Link: https://lore.kernel.org/all/20210103142726.GC30643@xsang-OptiPlex-9020/ Reported-by: Vito Caputo <vcaputo@...garu.com> Link: https://lore.kernel.org/lkml/20210921193249.el476vlhg5k6lfcq@shells.gnugeneration.com/ Reported-by: Jann Horn <jannh@...gle.com> Link: https://lore.kernel.org/lkml/CAG48ez2zC=+PuNgezH53HBPZ8CXU5H=vkWx7nJs60G8RXt3w0Q@mail.gmail.com/ Cc: stable@...r.kernel.org Signed-off-by: Kees Cook <keescook@...omium.org> --- fs/proc/base.c | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-) diff --git a/fs/proc/base.c b/fs/proc/base.c index 533d5836eb9a..1f394095eb88 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -67,6 +67,7 @@ #include <linux/mm.h> #include <linux/swap.h> #include <linux/rcupdate.h> +#include <linux/kallsyms.h> #include <linux/stacktrace.h> #include <linux/resource.h> #include <linux/module.h> @@ -386,17 +387,19 @@ static int proc_pid_wchan(struct seq_file *m, struct pid_namespace *ns, struct pid *pid, struct task_struct *task) { unsigned long wchan; + char symname[KSYM_NAME_LEN]; - if (ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS)) - wchan = get_wchan(task); - else - wchan = 0; + if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS)) + goto print0; - if (wchan) - seq_printf(m, "%ps", (void *) wchan); - else - seq_putc(m, '0'); + wchan = get_wchan(task); + if (wchan && !lookup_symbol_name(wchan, symname)) { + seq_puts(m, symname); + return 0; + } +print0: + seq_putc(m, '0'); return 0; } #endif /* CONFIG_KALLSYMS */ -- 2.30.2
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