From: Breno Leitao leitao@debian.org
[ Upstream commit 98fdaeb296f51ef08e727a7cc72e5b5c864c4f4d ]
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@debian.org Signed-off-by: Ingo Molnar mingo@kernel.org Reviewed-by: Pawan Gupta pawan.kumar.gupta@linux.intel.com Acked-by: Josh Poimboeuf jpoimboe@kernel.org Cc: Peter Zijlstra peterz@infradead.org Cc: David Kaplan David.Kaplan@amd.com Link: https://lore.kernel.org/r/20241031-x86_bugs_last_v2-v2-2-b7ff1dab840e@debian... Signed-off-by: Sasha Levin sashal@kernel.org --- 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 607a8937f1754..6e7b300b5c1d9 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -6243,6 +6243,8 @@
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 46bddb5bb15ff..e9f3103720396 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -1293,9 +1293,13 @@ 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; @@ -1308,7 +1312,7 @@ 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)) { @@ -1318,8 +1322,8 @@ 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)