[PATCH] sys_unshare: remove a broken CLONE_SIGHAND code

sys_unshare(CLONE_SIGHAND) is broken, the code under 'if (new_sigh)' is
never executed but very wrong. Just remove it to avoid a confusion,
task_lock() has nothing to do with ->sighand changing.

Also, change the comment in unshare_sighand(). Yes, CLONE_THREAD implies
CLONE_SIGHAND, but still it looks confusing. Also, we don't need to check
current->sighand != NULL.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/kernel/fork.c b/kernel/fork.c
index 7f2e31b..f387a13 100644 (file)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1544,15 +1544,13 @@ static int unshare_namespace(unsigned long unshare_flags, struct namespace **new
 }
 
 /*
- * Unsharing of sighand for tasks created with CLONE_SIGHAND is not
- * supported yet
+ * Unsharing of sighand is not supported yet
  */
 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
 {
        struct sighand_struct *sigh = current->sighand;
 
-       if ((unshare_flags & CLONE_SIGHAND) &&
-           (sigh && atomic_read(&sigh->count) > 1))
+       if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
                return -EINVAL;
        else
                return 0;
@@ -1626,7 +1624,7 @@ asmlinkage long sys_unshare(unsigned long unshare_flags)
        int err = 0;
        struct fs_struct *fs, *new_fs = NULL;
        struct namespace *ns, *new_ns = NULL;
-       struct sighand_struct *sigh, *new_sigh = NULL;
+       struct sighand_struct *new_sigh = NULL;
        struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
        struct files_struct *fd, *new_fd = NULL;
        struct sem_undo_list *new_ulist = NULL;
@@ -1671,7 +1669,7 @@ asmlinkage long sys_unshare(unsigned long unshare_flags)
                }
        }
 
-       if (new_fs || new_ns || new_sigh || new_mm || new_fd || new_ulist ||
+       if (new_fs || new_ns || new_mm || new_fd || new_ulist ||
                                new_uts || new_ipc) {
 
                task_lock(current);
@@ -1693,12 +1691,6 @@ asmlinkage long sys_unshare(unsigned long unshare_flags)
                        new_ns = ns;
                }
 
-               if (new_sigh) {
-                       sigh = current->sighand;
-                       rcu_assign_pointer(current->sighand, new_sigh);
-                       new_sigh = sigh;
-               }
-
                if (new_mm) {
                        mm = current->mm;
                        active_mm = current->active_mm;