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Commit 69f6a34b authored by Guenter Roeck's avatar Guenter Roeck Committed by Kees Cook
Browse files

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 dbd95212 ("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: dbd95212 ("seccomp: introduce writer locking")
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
parent c8d6637d

kernel/fork.c

+1 −1
Original line number Diff line number Diff line
@@ -1105,7 +1105,7 @@ static void copy_seccomp(struct task_struct *p) 
	 * needed because this new task is not yet running and cannot

	 * be racing exec.

	 */

	BUG_ON(!spin_is_locked(&current->sighand->siglock));

	assert_spin_locked(&current->sighand->siglock);



	/* Ref-count the new filter user, and assign it. */

	get_seccomp_filter(current);

kernel/seccomp.c

+5 −5
Original line number Diff line number Diff line
@@ -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;