seccomp: Replace BUG(!spin_is_locked()) with assert_spin_lock

Current upstream kernel hangs with mips and powerpc targets in
uniprocessor mode if SECCOMP is configured.

Bisect points to commit dbd952127d11 ("seccomp: introduce writer locking").
Turns out that code such as
	BUG_ON(!spin_is_locked(&list_lock));
can not be used in uniprocessor mode because spin_is_locked() always
returns false in this configuration, and that assert_spin_locked()
exists for that very purpose and must be used instead.

Fixes: dbd952127d11 ("seccomp: introduce writer locking")
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Kees Cook <keescook@chromium.org>

1 files changed, 5 insertions, 5 deletions

diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 25b0043f4755..44eb005c6695 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -203,7 +203,7 @@ static u32 seccomp_run_filters(int syscall)
 
 static inline bool seccomp_may_assign_mode(unsigned long seccomp_mode)
 {
-        BUG_ON(!spin_is_locked(&current->sighand->siglock));
+        assert_spin_locked(&current->sighand->siglock);
 
         if (current->seccomp.mode && current->seccomp.mode != seccomp_mode)
                 return false;
@@ -214,7 +214,7 @@ static inline bool seccomp_may_assign_mode(unsigned long seccomp_mode)
 static inline void seccomp_assign_mode(struct task_struct *task,
                                        unsigned long seccomp_mode)
 {
-        BUG_ON(!spin_is_locked(&task->sighand->siglock));
+        assert_spin_locked(&task->sighand->siglock);
 
         task->seccomp.mode = seccomp_mode;
         /*
@@ -253,7 +253,7 @@ static inline pid_t seccomp_can_sync_threads(void)
         struct task_struct *thread, *caller;
 
         BUG_ON(!mutex_is_locked(&current->signal->cred_guard_mutex));
-        BUG_ON(!spin_is_locked(&current->sighand->siglock));
+        assert_spin_locked(&current->sighand->siglock);
 
         /* Validate all threads being eligible for synchronization. */
         caller = current;
@@ -294,7 +294,7 @@ static inline void seccomp_sync_threads(void)
         struct task_struct *thread, *caller;
 
         BUG_ON(!mutex_is_locked(&current->signal->cred_guard_mutex));
-        BUG_ON(!spin_is_locked(&current->sighand->siglock));
+        assert_spin_locked(&current->sighand->siglock);
 
         /* Synchronize all threads. */
         caller = current;
@@ -464,7 +464,7 @@ static long seccomp_attach_filter(unsigned int flags,
         unsigned long total_insns;
         struct seccomp_filter *walker;
 
-        BUG_ON(!spin_is_locked(&current->sighand->siglock));
+        assert_spin_locked(&current->sighand->siglock);
 
         /* Validate resulting filter length. */
         total_insns = filter->prog->len;