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Message-ID: <20200226111827.GA16756@zn.tnic>
Date: Wed, 26 Feb 2020 12:18:27 +0100
From: Borislav Petkov <bp@...en8.de>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
Steven Rostedt <rostedt@...dmis.org>,
Brian Gerst <brgerst@...il.com>,
Juergen Gross <jgross@...e.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Arnd Bergmann <arnd@...db.de>,
Andy Lutomirski <luto@...nel.org>
Subject: Re: [patch 02/10] x86/mce: Disable tracing and kprobes on
do_machine_check()
On Tue, Feb 25, 2020 at 10:36:38PM +0100, Thomas Gleixner wrote:
> --- a/arch/x86/kernel/cpu/mce/core.c
> +++ b/arch/x86/kernel/cpu/mce/core.c
> @@ -1213,8 +1213,14 @@ static void __mc_scan_banks(struct mce *
> * On Intel systems this is entered on all CPUs in parallel through
> * MCE broadcast. However some CPUs might be broken beyond repair,
> * so be always careful when synchronizing with others.
> + *
> + * Tracing and kprobes are disabled: if we interrupted a kernel context
> + * with IF=1, we need to minimize stack usage. There are also recursion
> + * issues: if the machine check was due to a failure of the memory
> + * backing the user stack, tracing that reads the user stack will cause
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Had to read this a couple of times to parse that formulation properly.
Make that
"... backing the user stack, tracing code which accesses same user stack
will potentially cause an infinite recursion."
With that:
Reviewed-by: Borislav Petkov <bp@...e.de>
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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