[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <d290202d-a72d-0821-9edf-efbecf6f6cef@linux.com>
Date: Wed, 29 Sep 2021 22:01:33 +0300
From: Alexander Popov <alex.popov@...ux.com>
To: Jonathan Corbet <corbet@....net>, Paul McKenney <paulmck@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Thomas Gleixner <tglx@...utronix.de>, Peter Zijlstra <peterz@...radead.org>,
Joerg Roedel <jroedel@...e.de>, Maciej Rozycki <macro@...am.me.uk>,
Muchun Song <songmuchun@...edance.com>,
Viresh Kumar <viresh.kumar@...aro.org>, Robin Murphy <robin.murphy@....com>,
Randy Dunlap <rdunlap@...radead.org>, Lu Baolu <baolu.lu@...ux.intel.com>,
Petr Mladek <pmladek@...e.com>, Kees Cook <keescook@...omium.org>,
Luis Chamberlain <mcgrof@...nel.org>, Wei Liu <wl@....org>,
John Ogness <john.ogness@...utronix.de>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Alexey Kardashevskiy <aik@...abs.ru>,
Christophe Leroy <christophe.leroy@...roup.eu>, Jann Horn
<jannh@...gle.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Mark Rutland <mark.rutland@....com>, Andy Lutomirski <luto@...nel.org>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Steven Rostedt <rostedt@...dmis.org>, Thomas Garnier <thgarnie@...gle.com>,
Will Deacon <will.deacon@....com>, Ard Biesheuvel
<ard.biesheuvel@...aro.org>, Laura Abbott <labbott@...hat.com>,
David S Miller <davem@...emloft.net>, Borislav Petkov <bp@...en8.de>,
kernel-hardening@...ts.openwall.com, linux-hardening@...r.kernel.org,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: notify@...nel.org
Subject: Re: [PATCH] Introduce the pkill_on_warn boot parameter
On 29.09.2021 21:58, Alexander Popov wrote:
> Currently, the Linux kernel provides two types of reaction to kernel
> warnings:
> 1. Do nothing (by default),
> 2. Call panic() if panic_on_warn is set. That's a very strong reaction,
> so panic_on_warn is usually disabled on production systems.
>
> From a safety point of view, the Linux kernel misses a middle way of
> handling kernel warnings:
> - The kernel should stop the activity that provokes a warning,
> - But the kernel should avoid complete denial of service.
>
> From a security point of view, kernel warning messages provide a lot of
> useful information for attackers. Many GNU/Linux distributions allow
> unprivileged users to read the kernel log, so attackers use kernel
> warning infoleak in vulnerability exploits. See the examples:
> https://a13xp0p0v.github.io/2020/02/15/CVE-2019-18683.html
> https://a13xp0p0v.github.io/2021/02/09/CVE-2021-26708.html
>
> Let's introduce the pkill_on_warn boot parameter.
> If this parameter is set, the kernel kills all threads in a process
> that provoked a kernel warning. This behavior is reasonable from a safety
> point of view described above. It is also useful for kernel security
> hardening because the system kills an exploit process that hits a
> kernel warning.
>
> Signed-off-by: Alexander Popov <alex.popov@...ux.com>
This patch was tested using CONFIG_LKDTM.
The kernel kills a process that performs this:
echo WARNING > /sys/kernel/debug/provoke-crash/DIRECT
If you are fine with this approach, I will prepare a patch adding the
pkill_on_warn sysctl.
Best regards,
Alexander
> ---
> Documentation/admin-guide/kernel-parameters.txt | 4 ++++
> kernel/panic.c | 5 +++++
> 2 files changed, 9 insertions(+)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 91ba391f9b32..86c748907666 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -4112,6 +4112,10 @@
> pirq= [SMP,APIC] Manual mp-table setup
> See Documentation/x86/i386/IO-APIC.rst.
>
> + pkill_on_warn= Kill all threads in a process that provoked a
> + kernel warning.
> + Format: { "0" | "1" }
> +
> plip= [PPT,NET] Parallel port network link
> Format: { parport<nr> | timid | 0 }
> See also Documentation/admin-guide/parport.rst.
> diff --git a/kernel/panic.c b/kernel/panic.c
> index cefd7d82366f..47b728bfb1d3 100644
> --- a/kernel/panic.c
> +++ b/kernel/panic.c
> @@ -53,6 +53,7 @@ static int pause_on_oops_flag;
> static DEFINE_SPINLOCK(pause_on_oops_lock);
> bool crash_kexec_post_notifiers;
> int panic_on_warn __read_mostly;
> +int pkill_on_warn __read_mostly;
> unsigned long panic_on_taint;
> bool panic_on_taint_nousertaint = false;
>
> @@ -610,6 +611,9 @@ void __warn(const char *file, int line, void *caller, unsigned taint,
>
> print_oops_end_marker();
>
> + if (pkill_on_warn && system_state >= SYSTEM_RUNNING)
> + do_group_exit(SIGKILL);
> +
> /* Just a warning, don't kill lockdep. */
> add_taint(taint, LOCKDEP_STILL_OK);
> }
> @@ -694,6 +698,7 @@ core_param(panic, panic_timeout, int, 0644);
> core_param(panic_print, panic_print, ulong, 0644);
> core_param(pause_on_oops, pause_on_oops, int, 0644);
> core_param(panic_on_warn, panic_on_warn, int, 0644);
> +core_param(pkill_on_warn, pkill_on_warn, int, 0644);
> core_param(crash_kexec_post_notifiers, crash_kexec_post_notifiers, bool, 0644);
>
> static int __init oops_setup(char *s)
>
Powered by blists - more mailing lists
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
