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seccomp: Enable speculation flaw mitigations 

When speculation flaw mitigations are opt-in (via prctl), using seccomp
will automatically opt-in to these protections, since using seccomp
indicates at least some level of sandboxing is desired.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Kees Cook 2018-05-01 15:07:31 -07:00 committed by Thomas Gleixner
parent fae1fa0fc6
commit 5c3070890d
1 changed files with 17 additions and 0 deletions
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17
kernel/seccomp.c
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@ -19,6 +19,8 @@
#include <linux/compat.h> #include <linux/compat.h>
#include <linux/coredump.h> #include <linux/coredump.h>
#include <linux/kmemleak.h> #include <linux/kmemleak.h>
#include <linux/nospec.h>
#include <linux/prctl.h>
#include <linux/sched.h> #include <linux/sched.h>
#include <linux/sched/task_stack.h> #include <linux/sched/task_stack.h>
#include <linux/seccomp.h> #include <linux/seccomp.h>
@ -227,6 +229,19 @@ static inline bool seccomp_may_assign_mode(unsigned long seccomp_mode)
return true; return true;
} }
/*
* If a given speculation mitigation is opt-in (prctl()-controlled),
* select it, by disabling speculation (enabling mitigation).
*/
static inline void spec_mitigate(struct task_struct *task,
unsigned long which)
{
int state = arch_prctl_spec_ctrl_get(task, which);
if (state > 0 && (state & PR_SPEC_PRCTL))
arch_prctl_spec_ctrl_set(task, which, PR_SPEC_DISABLE);
}
static inline void seccomp_assign_mode(struct task_struct *task, static inline void seccomp_assign_mode(struct task_struct *task,
unsigned long seccomp_mode) unsigned long seccomp_mode)
{ {
@ -238,6 +253,8 @@ static inline void seccomp_assign_mode(struct task_struct *task,
* filter) is set. * filter) is set.
*/ */
smp_mb__before_atomic(); smp_mb__before_atomic();
/* Assume seccomp processes want speculation flaw mitigation. */
spec_mitigate(task, PR_SPEC_STORE_BYPASS);
set_tsk_thread_flag(task, TIF_SECCOMP); set_tsk_thread_flag(task, TIF_SECCOMP);
} }