Messages in this thread Patch in this message |  | | | Date | Mon, 07 Nov 2005 21:12:43 +0300 | | From | Oleg Nesterov <> | | Subject | [PATCH] fix de_thread() vs send_group_sigqueue() race |
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When non-leader thread does exec, de_thread calls release_task(leader) before calling exit_itimers(). If local timer interrupt happens in between, it can oops in send_group_sigqueue() while taking ->sighand->siglock == NULL.
However, we can't change send_group_sigqueue() to check p->signal != NULL, because sys_timer_create() does get_task_struct() only in SIGEV_THREAD_ID case. So it is possible that this task_struct was already freed and we can't trust p->signal.
This patch changes de_thread() so that leader released after exit_itimers() call.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
--- 2.6.14/fs/exec.c~ 2005-09-21 21:08:33.000000000 +0400 +++ 2.6.14/fs/exec.c 2005-11-07 23:54:42.000000000 +0300 @@ -593,6 +593,7 @@ static inline int de_thread(struct task_ struct signal_struct *sig = tsk->signal; struct sighand_struct *newsighand, *oldsighand = tsk->sighand; spinlock_t *lock = &oldsighand->siglock; + struct task_struct *leader = NULL; int count; /* @@ -668,7 +669,7 @@ static inline int de_thread(struct task_ * and to assume its PID: */ if (!thread_group_leader(current)) { - struct task_struct *leader = current->group_leader, *parent; + struct task_struct *parent; struct dentry *proc_dentry1, *proc_dentry2; unsigned long exit_state, ptrace; @@ -677,6 +678,7 @@ static inline int de_thread(struct task_ * It should already be zombie at this point, most * of the time. */ + leader = current->group_leader; while (leader->exit_state != EXIT_ZOMBIE) yield(); @@ -736,7 +738,6 @@ static inline int de_thread(struct task_ proc_pid_flush(proc_dentry2); BUG_ON(exit_state != EXIT_ZOMBIE); - release_task(leader); } /* @@ -746,8 +747,11 @@ static inline int de_thread(struct task_ sig->flags = 0; no_thread_group: - BUG_ON(atomic_read(&sig->count) != 1); exit_itimers(sig); + if (leader) + release_task(leader); + + BUG_ON(atomic_read(&sig->count) != 1); if (atomic_read(&oldsighand->count) == 1) { /* - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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