From: Geert Uytterhoeven geert@linux-m68k.org
commit 1bf72720281770162c87990697eae1ba2f1d917a upstream.
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: 98af8452945c5565 ("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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/cpu.c | 3 +++ 1 file changed, 3 insertions(+)
--- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -2315,6 +2315,9 @@ static int __init mitigations_parse_cmdl 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; }