Re: [PATCH] seccomp: Replace BUG(!spin_is_locked()) with assert_spin_lock

[Guenter Roeck]

On 08/10/2014 11:19 PM, sanjeev sharma wrote:

Hello Guenter Roeck

The same thing should be taken care in futex.c

That is using WARN_ON_SMP which is provided for that purpose.

Guenter

Regards
Sanjeev Sharma


On Mon, Aug 11, 2014 at 9:20 AM, Guenter Roeck <li...@roeck-us.net 
<mailto:li...@roeck-us.net>> wrote:

    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 <keesc...@chromium.org <mailto:keesc...@chromium.org>>
    Signed-off-by: Guenter Roeck <li...@roeck-us.net 
<mailto:li...@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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