When a task changes its dumpability, arch_update_spec_ctrl_restriction() is called to place restriction on the task's speculative execution according to dumpability changes.
Implements arch_update_spec_restriction() for x86. Use STIBP to restrict speculative execution when running a task set to non-dumpable, or clear the restriction if the task is set to dumpable. Signed-off-by: Tim Chen <[email protected]> --- Documentation/admin-guide/kernel-parameters.txt | 3 ++- arch/x86/kernel/cpu/bugs.c | 21 +++++++++++++++++++-- 2 files changed, 21 insertions(+), 3 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 9c306e3..102f9a1 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -4221,7 +4221,8 @@ vulnerability. off - Unconditionally disable mitigations - lite - Protect tasks which have requested restricted + lite - Protect tasks which are marked non-dumpable + and tasks which have requested restricted indirect branch speculation via the PR_SET_SPECULATION_CTRL prctl(). strict - Protect all processes diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 8f5187e..e7f9334 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -14,6 +14,7 @@ #include <linux/module.h> #include <linux/nospec.h> #include <linux/prctl.h> +#include <linux/coredump.h> #include <asm/spec-ctrl.h> #include <asm/cmdline.h> @@ -152,7 +153,7 @@ static const char *spectre_v2_strings[] = { static const char *spectre_v2_app2app_strings[] = { [SPECTRE_V2_APP2APP_NONE] = "App-App Vulnerable", - [SPECTRE_V2_APP2APP_LITE] = "App-App Mitigation: Protect branch speculation restricted tasks", + [SPECTRE_V2_APP2APP_LITE] = "App-App Mitigation: Protect non-dumpable and branch speculation restricted tasks", [SPECTRE_V2_APP2APP_STRICT] = "App-App Mitigation: Full app to app attack protection", }; @@ -779,13 +780,29 @@ static void set_task_stibp(struct task_struct *tsk, bool stibp_on) if (stibp_on) update = !test_and_set_tsk_thread_flag(tsk, TIF_STIBP); - else + else if (!task_spec_indir_branch_disable(tsk)) update = test_and_clear_tsk_thread_flag(tsk, TIF_STIBP); if (tsk == current && update) speculation_ctrl_update_current(); } +int arch_update_spec_restriction(struct task_struct *task) +{ + if (!static_branch_unlikely(&spectre_v2_app_lite)) + return 0; + + if (!task->mm) + return -EINVAL; + + if (get_dumpable(task->mm) != SUID_DUMP_USER) + set_task_stibp(task, true); + else + set_task_stibp(task, false); + + return 0; +} + static int indir_branch_prctl_set(struct task_struct *task, unsigned long ctrl) { switch (ctrl) { -- 2.9.4
