signals: move cred_guard_mutex from task_struct to signal_struct
Oleg Nesterov pointed out we have to prevent multiple-threads-inside-exec
itself and we can reuse ->cred_guard_mutex for it. Yes, concurrent
execve() has no worth.
Let's move ->cred_guard_mutex from task_struct to signal_struct. It
naturally prevent multiple-threads-inside-exec.
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Roland McGrath <roland@redhat.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/cred.c b/kernel/cred.c
index 9a3e226..6a1aa00 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -325,7 +325,7 @@
/*
* Prepare credentials for current to perform an execve()
- * - The caller must hold current->cred_guard_mutex
+ * - The caller must hold ->cred_guard_mutex
*/
struct cred *prepare_exec_creds(void)
{
@@ -384,8 +384,6 @@
struct cred *new;
int ret;
- mutex_init(&p->cred_guard_mutex);
-
if (
#ifdef CONFIG_KEYS
!p->cred->thread_keyring &&
diff --git a/kernel/fork.c b/kernel/fork.c
index e87aaaa..3b159c5 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -908,6 +908,8 @@
sig->oom_adj = current->signal->oom_adj;
sig->oom_score_adj = current->signal->oom_score_adj;
+ mutex_init(&sig->cred_guard_mutex);
+
return 0;
}
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index ea7ce02..99bbaa3 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -181,7 +181,7 @@
* under ptrace.
*/
retval = -ERESTARTNOINTR;
- if (mutex_lock_interruptible(&task->cred_guard_mutex))
+ if (mutex_lock_interruptible(&task->signal->cred_guard_mutex))
goto out;
task_lock(task);
@@ -208,7 +208,7 @@
unlock_tasklist:
write_unlock_irq(&tasklist_lock);
unlock_creds:
- mutex_unlock(&task->cred_guard_mutex);
+ mutex_unlock(&task->signal->cred_guard_mutex);
out:
return retval;
}