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") Cc: stable@vger.kernel.org Signed-off-by: Geert Uytterhoeven geert@linux-m68k.org --- kernel/cpu.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/kernel/cpu.c b/kernel/cpu.c index f2ef10460698e9ec..8458fda00e6ddb88 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -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; }