diff options
| author | Oleg Nesterov <oleg@tv-sign.ru> | 2008-02-04 22:27:24 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2008-02-05 09:44:07 -0800 |
| commit | ed5d2cac114202fe2978a9cbcab8f5032796d538 (patch) | |
| tree | aa9aaea1aa0945bd9159685d1b04897d105a90c9 /fs/exec.c | |
| parent | f558b7e408026eb3c6afcd0e8fc1f7fe31195a6a (diff) | |
| download | lwn-ed5d2cac114202fe2978a9cbcab8f5032796d538.tar.gz lwn-ed5d2cac114202fe2978a9cbcab8f5032796d538.zip | |
exec: rework the group exit and fix the race with kill
As Roland pointed out, we have the very old problem with exec. de_thread()
sets SIGNAL_GROUP_EXIT, kills other threads, changes ->group_leader and then
clears signal->flags. All signals (even fatal ones) sent in this window
(which is not too small) will be lost.
With this patch exec doesn't abuse SIGNAL_GROUP_EXIT. signal_group_exit(),
the new helper, should be used to detect exit_group() or exec() in progress.
It can have more users, but this patch does only strictly necessary changes.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Davide Libenzi <davidel@xmailserver.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Robin Holt <holt@sgi.com>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/exec.c')
| -rw-r--r-- | fs/exec.c | 13 |
1 files changed, 4 insertions, 9 deletions
diff --git a/fs/exec.c b/fs/exec.c index 966c5c5b6741..be923e4bc389 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -760,7 +760,7 @@ static int de_thread(struct task_struct *tsk) */ read_lock(&tasklist_lock); spin_lock_irq(lock); - if (sig->flags & SIGNAL_GROUP_EXIT) { + if (signal_group_exit(sig)) { /* * Another group action in progress, just * return so that the signal is processed. @@ -778,6 +778,7 @@ static int de_thread(struct task_struct *tsk) if (unlikely(tsk->group_leader == task_child_reaper(tsk))) task_active_pid_ns(tsk)->child_reaper = tsk; + sig->group_exit_task = tsk; zap_other_threads(tsk); read_unlock(&tasklist_lock); @@ -802,7 +803,6 @@ static int de_thread(struct task_struct *tsk) } sig->notify_count = count; - sig->group_exit_task = tsk; while (atomic_read(&sig->count) > count) { __set_current_state(TASK_UNINTERRUPTIBLE); spin_unlock_irq(lock); @@ -871,15 +871,10 @@ static int de_thread(struct task_struct *tsk) leader->exit_state = EXIT_DEAD; write_unlock_irq(&tasklist_lock); - } + } sig->group_exit_task = NULL; sig->notify_count = 0; - /* - * There may be one thread left which is just exiting, - * but it's safe to stop telling the group to kill themselves. - */ - sig->flags = 0; no_thread_group: exit_itimers(sig); @@ -1549,7 +1544,7 @@ static inline int zap_threads(struct task_struct *tsk, struct mm_struct *mm, int err = -EAGAIN; spin_lock_irq(&tsk->sighand->siglock); - if (!(tsk->signal->flags & SIGNAL_GROUP_EXIT)) { + if (!signal_group_exit(tsk->signal)) { tsk->signal->group_exit_code = exit_code; zap_process(tsk); err = 0; |