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 Acked-by: Peter Zijlstra Signed-off-by: Andrew Morton --- kernel/fork.c | 16 ++++------------ 1 file changed, 4 insertions(+), 12 deletions(-) diff -puN kernel/fork.c~sys_unshare-remove-a-broken-clone_sighand-code kernel/fork.c --- a/kernel/fork.c~sys_unshare-remove-a-broken-clone_sighand-code +++ a/kernel/fork.c @@ -1546,15 +1546,13 @@ static int unshare_namespace(unsigned lo } /* - * 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; @@ -1628,7 +1626,7 @@ asmlinkage long sys_unshare(unsigned lon 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; @@ -1673,7 +1671,7 @@ asmlinkage long sys_unshare(unsigned lon } } - 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); @@ -1695,12 +1693,6 @@ asmlinkage long sys_unshare(unsigned lon 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; _