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 <tim.c.chen@xxxxxxxxxxxxxxx>
---
Documentation/admin-guide/kernel-parameters.txt | 3 ++-
arch/x86/kernel/cpu/bugs.c | 23 ++++++++++++++++++++---
2 files changed, 22 insertions(+), 4 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 89b193c..3979b12 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4229,7 +4229,8 @@
If the CPU is vulnerable, the default mitigation
is architecture and Kconfig dependent. See below.
prctl - Enable mitigations per thread by restricting
- indirect branch speculation via prctl.
+ indirect branch speculation via prctl or setting
+ the thread as non-dumpable.
Mitigation for a thread is not enabled by default to
avoid mitigation overhead. The state of
of the control is inherited on fork.
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index f349b3f..6cd64445 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>
@@ -153,8 +154,8 @@ static const char *spectre_v2_strings[] = {
static const char *spectre_v2_app2app_strings[] = {
[SPECTRE_V2_APP2APP_NONE] = "App-App Vulnerable",
[SPECTRE_V2_APP2APP_STRICT] = "App-App Mitigation: Full app to app attack protection",
- [SPECTRE_V2_APP2APP_PRCTL] = "App-App Mitigation: Protect branch speculation restricted tasks",
- [SPECTRE_V2_APP2APP_SECCOMP] = "App-App Mitigation: Protect branch speculation restricted and seccomp tasks",
+ [SPECTRE_V2_APP2APP_PRCTL] = "App-App Mitigation: Protect non-dumpable and branch speculation restricted tasks",
+ [SPECTRE_V2_APP2APP_SECCOMP] = "App-App Mitigation: Protect non-dumpable, branch speculation restricted and seccomp tasks",
};
/* Lightweight mitigation: mitigate only tasks with TIF_SPEC_INDIR_BRANCH */
@@ -792,13 +793,29 @@ static void set_task_restrict_indir_branch(struct task_struct *tsk, bool restric
if (restrict_on)
update = !test_and_set_tsk_thread_flag(tsk, TIF_SPEC_INDIR_BRANCH);
- else
+ else if (!task_spec_indir_branch_disable(tsk))
update = test_and_clear_tsk_thread_flag(tsk, TIF_SPEC_INDIR_BRANCH);
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_restrict_indir_branch(task, true);
+ else
+ set_task_restrict_indir_branch(task, false);
+
+ return 0;
+}
+
static int indir_branch_prctl_set(struct task_struct *task, unsigned long ctrl)
{
switch (ctrl) {
--
2.9.4
