Commit 1bf72720 authored May 16, 2019 by Geert Uytterhoeven Committed by Thomas Gleixner Jun 26, 2019

cpu/speculation: Warn on unsupported mitigations= parameter



Currently, if the user specifies an unsupported mitigation strategy on the
kernel command line, it will be ignored silently.  The code will fall back
to the default strategy, possibly leaving the system more vulnerable than
expected.

This may happen due to e.g. a simple typo, or, for a stable kernel release,
because not all mitigation strategies have been backported.

Inform the user by printing a message.

Fixes: 98af8452 ("cpu/speculation: Add 'mitigations=' cmdline option")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ben Hutchings <ben@decadent.org.uk>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20190516070935.22546-1-geert@linux-m68k.org

parent 4b972a01

kernel/cpu.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -2339,6 +2339,9 @@ static int __init mitigations_parse_cmdline(char *arg)
		cpu_mitigations = CPU_MITIGATIONS_AUTO;
		else if (!strcmp(arg, "auto,nosmt"))
		cpu_mitigations = CPU_MITIGATIONS_AUTO_NOSMT;
		else
		pr_crit("Unsupported mitigations=%s, system may still be vulnerable\n",
		arg);

		return 0;
		}

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