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| author | Oleg Nesterov <oleg@tv-sign.ru> | 2005-11-07 21:12:43 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2005-11-08 12:58:38 -0800 |
| commit | 329f7dba5f7dc3bc9a30ad00cf373d2e83115aa1 (patch) | |
| tree | 3d8c8b2fd07ad2c1df959421121451207373f78f | |
| parent | a52e8381c430896d3bd6065a34fda99cb5c74c82 (diff) | |
| download | lwn-329f7dba5f7dc3bc9a30ad00cf373d2e83115aa1.tar.gz lwn-329f7dba5f7dc3bc9a30ad00cf373d2e83115aa1.zip | |
[PATCH] fix de_thread() vs send_group_sigqueue() race
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>
Acked-by: Chris Wright <chrisw@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
| -rw-r--r-- | fs/exec.c | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/fs/exec.c b/fs/exec.c index cd6c574557dc..5a4e3acc2e9f 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -590,6 +590,7 @@ static inline int de_thread(struct task_struct *tsk) 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; /* @@ -665,7 +666,7 @@ static inline int de_thread(struct task_struct *tsk) * 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; @@ -674,6 +675,7 @@ static inline int de_thread(struct task_struct *tsk) * It should already be zombie at this point, most * of the time. */ + leader = current->group_leader; while (leader->exit_state != EXIT_ZOMBIE) yield(); @@ -733,7 +735,6 @@ static inline int de_thread(struct task_struct *tsk) proc_pid_flush(proc_dentry2); BUG_ON(exit_state != EXIT_ZOMBIE); - release_task(leader); } /* @@ -743,8 +744,11 @@ static inline int de_thread(struct task_struct *tsk) 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) { /* |