Change the default value of spectre v2 in user mode to respect the
CONFIG_MITIGATION_SPECTRE_V2 config option.
Currently, user mode spectre v2 is set to auto
(SPECTRE_V2_USER_CMD_AUTO) by default, even if
CONFIG_MITIGATION_SPECTRE_V2 is disabled.
Set the spectre_v2 value to auto (SPECTRE_V2_USER_CMD_AUTO) if the
Spectre v2 config (CONFIG_MITIGATION_SPECTRE_V2) is enabled, otherwise
set the value to none (SPECTRE_V2_USER_CMD_NONE).
Important to say the command line argument "spectre_v2_user" overwrites
the default value in both cases.
When CONFIG_MITIGATION_SPECTRE_V2 is not set, users have the flexibility
to opt-in for specific mitigations independently. In this scenario,
setting spectre_v2= will not enable spectre_v2_user=, and command line
options spectre_v2_user and spectre_v2 are independent when
CONFIG_MITIGATION_SPECTRE_V2=n.
Signed-off-by: Breno Leitao <leitao@xxxxxxxxxx>
Acked-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Reviewed-by: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx>
---
Documentation/admin-guide/kernel-parameters.txt | 2 ++
arch/x86/kernel/cpu/bugs.c | 10 +++++++---
2 files changed, 9 insertions(+), 3 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 1518343bbe2237f1d577df5656339d6224b769be..f8bc02cd10ec3012c478e12e90bad85d9f70d9ed 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -6241,6 +6241,8 @@
Selecting 'on' will also enable the mitigation
against user space to user space task attacks.
+ Selecting specific mitigation does not force enable
+ user mitigations.
Selecting 'off' will disable both the kernel and
the user space protections.
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index ceaa5f0c742025a62aa564aaa9cdfa1fe86e681c..236c691c3fd2ac7d41c494d5c7fbc844d11ae82f 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1294,9 +1294,13 @@ static __ro_after_init enum spectre_v2_mitigation_cmd spectre_v2_cmd;
static enum spectre_v2_user_cmd __init
spectre_v2_parse_user_cmdline(void)
{
+ enum spectre_v2_user_cmd mode;
char arg[20];
int ret, i;
+ mode = IS_ENABLED(CONFIG_MITIGATION_SPECTRE_V2) ?
+ SPECTRE_V2_USER_CMD_AUTO : SPECTRE_V2_USER_CMD_NONE;
+
switch (spectre_v2_cmd) {
case SPECTRE_V2_CMD_NONE:
return SPECTRE_V2_USER_CMD_NONE;
@@ -1309,7 +1313,7 @@ spectre_v2_parse_user_cmdline(void)
ret = cmdline_find_option(boot_command_line, "spectre_v2_user",
arg, sizeof(arg));
if (ret < 0)
- return SPECTRE_V2_USER_CMD_AUTO;
+ return mode;
for (i = 0; i < ARRAY_SIZE(v2_user_options); i++) {
if (match_option(arg, ret, v2_user_options[i].option)) {
@@ -1319,8 +1323,8 @@ spectre_v2_parse_user_cmdline(void)
}
}
- pr_err("Unknown user space protection option (%s). Switching to AUTO select\n", arg);
- return SPECTRE_V2_USER_CMD_AUTO;
+ pr_err("Unknown user space protection option (%s). Switching to default\n", arg);
+ return mode;
}
static inline bool spectre_v2_in_ibrs_mode(enum spectre_v2_mitigation mode)
--
2.43.5
