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Subject[PATCH] seccomp: Replace BUG(!spin_is_locked()) with assert_spin_lock
Date
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>
---
kernel/fork.c | 2 +-
kernel/seccomp.c | 10 +++++-----
2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index 1380d8a..0cf9cdb 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -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);
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 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;
--
1.9.1


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