commit 69f6a34bdeea4fec50bb90619bc9602973119572
author Guenter Roeck <linux@roeck-us.net> Sun Aug 10 20:50:30 2014 -0700
committer Kees Cook <keescook@chromium.org> Mon Aug 11 13:29:12 2014 -0700
tree 8fb595069ac3490438244ca28076b7c1837f93d8
parent c8d6637d0497d62093dbba0694c7b3a80b79bfe1

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>

kernel/seccomp.c

diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 25b0043..44eb005 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -203,7 +203,7 @@
 
 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 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 @@
 	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 @@
 	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 @@
 	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;