seccomp: Add filter flag to opt-out of SSB mitigation

[mirror_ubuntu-artful-kernel.git] / kernel / seccomp.c

diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 494f98e07b2d71d2b14ceb62bd351813bbd993cb..bb1cc737456eaf86014d2e9f395b188d75cba3bb 100644 (file)
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -241,7 +241,8 @@ static inline void spec_mitigate(struct task_struct *task,
 }
 
 static inline void seccomp_assign_mode(struct task_struct *task,
-                                      unsigned long seccomp_mode)
+                                      unsigned long seccomp_mode,
+                                      unsigned long flags)
 {
        assert_spin_locked(&task->sighand->siglock);
 
@@ -251,8 +252,9 @@ static inline void seccomp_assign_mode(struct task_struct *task,
         * filter) is set.
         */
        smp_mb__before_atomic();
-       /* Assume seccomp processes want speculation flaw mitigation. */
-       spec_mitigate(task, PR_SPEC_STORE_BYPASS);
+       /* Assume default seccomp processes want spec flaw mitigation. */
+       if ((flags & SECCOMP_FILTER_FLAG_SPEC_ALLOW) == 0)
+               spec_mitigate(task, PR_SPEC_STORE_BYPASS);
        set_tsk_thread_flag(task, TIF_SECCOMP);
 }
 
@@ -320,7 +322,7 @@ static inline pid_t seccomp_can_sync_threads(void)
  * without dropping the locks.
  *
  */
-static inline void seccomp_sync_threads(void)
+static inline void seccomp_sync_threads(unsigned long flags)
 {
        struct task_struct *thread, *caller;
 
@@ -361,7 +363,8 @@ static inline void seccomp_sync_threads(void)
                 * allow one thread to transition the other.
                 */
                if (thread->seccomp.mode == SECCOMP_MODE_DISABLED)
-                       seccomp_assign_mode(thread, SECCOMP_MODE_FILTER);
+                       seccomp_assign_mode(thread, SECCOMP_MODE_FILTER,
+                                           flags);
        }
 }
 
@@ -484,7 +487,7 @@ static long seccomp_attach_filter(unsigned int flags,
 
        /* Now that the new filter is in place, synchronize to all threads. */
        if (flags & SECCOMP_FILTER_FLAG_TSYNC)
-               seccomp_sync_threads();
+               seccomp_sync_threads(flags);
 
        return 0;
 }
@@ -821,7 +824,7 @@ static long seccomp_set_mode_strict(void)
 #ifdef TIF_NOTSC
        disable_TSC();
 #endif
-       seccomp_assign_mode(current, seccomp_mode);
+       seccomp_assign_mode(current, seccomp_mode, 0);
        ret = 0;
 
 out:
@@ -879,7 +882,7 @@ static long seccomp_set_mode_filter(unsigned int flags,
        /* Do not free the successfully attached filter. */
        prepared = NULL;
 
-       seccomp_assign_mode(current, seccomp_mode);
+       seccomp_assign_mode(current, seccomp_mode, flags);
 out:
        spin_unlock_irq(&current->sighand->siglock);
        if (flags & SECCOMP_FILTER_FLAG_TSYNC)