Commit 02169155 authored by Eric W. Biederman's avatar Eric W. Biederman

exec: Factor unshare_sighand out of de_thread and call it separately

This makes the code clearer and makes it easier to implement a mutex
that is not taken over any locations that may block indefinitely waiting
for userspace.
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
Reviewed-by: default avatarBernd Edlinger <bernd.edlinger@hotmail.de>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Acked-by: default avatarChristian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: default avatarKirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: default avatarBernd Edlinger <bernd.edlinger@hotmail.de>
Signed-off-by: default avatarEric W. Biederman <ebiederm@xmission.com>
parent 2ca7be7d
...@@ -1194,6 +1194,23 @@ static int de_thread(struct task_struct *tsk) ...@@ -1194,6 +1194,23 @@ static int de_thread(struct task_struct *tsk)
flush_itimer_signals(); flush_itimer_signals();
#endif #endif
BUG_ON(!thread_group_leader(tsk));
return 0;
killed:
/* protects against exit_notify() and __exit_signal() */
read_lock(&tasklist_lock);
sig->group_exit_task = NULL;
sig->notify_count = 0;
read_unlock(&tasklist_lock);
return -EAGAIN;
}
static int unshare_sighand(struct task_struct *me)
{
struct sighand_struct *oldsighand = me->sighand;
if (refcount_read(&oldsighand->count) != 1) { if (refcount_read(&oldsighand->count) != 1) {
struct sighand_struct *newsighand; struct sighand_struct *newsighand;
/* /*
...@@ -1210,23 +1227,13 @@ static int de_thread(struct task_struct *tsk) ...@@ -1210,23 +1227,13 @@ static int de_thread(struct task_struct *tsk)
write_lock_irq(&tasklist_lock); write_lock_irq(&tasklist_lock);
spin_lock(&oldsighand->siglock); spin_lock(&oldsighand->siglock);
rcu_assign_pointer(tsk->sighand, newsighand); rcu_assign_pointer(me->sighand, newsighand);
spin_unlock(&oldsighand->siglock); spin_unlock(&oldsighand->siglock);
write_unlock_irq(&tasklist_lock); write_unlock_irq(&tasklist_lock);
__cleanup_sighand(oldsighand); __cleanup_sighand(oldsighand);
} }
BUG_ON(!thread_group_leader(tsk));
return 0; return 0;
killed:
/* protects against exit_notify() and __exit_signal() */
read_lock(&tasklist_lock);
sig->group_exit_task = NULL;
sig->notify_count = 0;
read_unlock(&tasklist_lock);
return -EAGAIN;
} }
char *__get_task_comm(char *buf, size_t buf_size, struct task_struct *tsk) char *__get_task_comm(char *buf, size_t buf_size, struct task_struct *tsk)
...@@ -1264,13 +1271,19 @@ int flush_old_exec(struct linux_binprm * bprm) ...@@ -1264,13 +1271,19 @@ int flush_old_exec(struct linux_binprm * bprm)
int retval; int retval;
/* /*
* Make sure we have a private signal table and that * Make this the only thread in the thread group.
* we are unassociated from the previous thread group.
*/ */
retval = de_thread(me); retval = de_thread(me);
if (retval) if (retval)
goto out; goto out;
/*
* Make the signal table private.
*/
retval = unshare_sighand(me);
if (retval)
goto out;
/* /*
* Must be called _before_ exec_mmap() as bprm->mm is * Must be called _before_ exec_mmap() as bprm->mm is
* not visibile until then. This also enables the update * not visibile until then. This also enables the update
......
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