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; }
On Thu, 16 May 2019, Geert Uytterhoeven wrote:
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.
Honestly, I am not convinced. We are not doing this for vast majority of other cmdline options either, if for any at all.
Thanks,
* Jiri Kosina jikos@kernel.org wrote:
On Thu, 16 May 2019, Geert Uytterhoeven wrote:
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.
Honestly, I am not convinced. We are not doing this for vast majority of other cmdline options either, if for any at all.
That's really a weakness - I've been bitten by this previously: I typoed or mis-remembered a command line option and didn't have it while I thought I had it.
Our boot-commandline library is pretty user-unfriendly.
Thanks,
Ingo
On Thu, May 16, 2019 at 09:09:35AM +0200, Geert Uytterhoeven wrote:
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; } -- 2.17.1
Acked-by: Josh Poimboeuf jpoimboe@redhat.com
linux-stable-mirror@lists.linaro.org
-
Geert Uytterhoeven -
Ingo Molnar -
Jiri Kosina -
Josh Poimboeuf