[PATCH] fix zap_thread's ptrace related problems
1. The tracee can go from ptrace_stop() to do_signal_stop()
after __ptrace_unlink(p).
2. It is unsafe to __ptrace_unlink(p) while p->parent may wait
for tasklist_lock in ptrace_detach().
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/exec.c b/fs/exec.c
index 055378d..0e1c950 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1403,7 +1403,7 @@
do_each_thread(g,p) {
if (mm == p->mm && p != tsk &&
p->ptrace && p->parent->mm == mm) {
- __ptrace_unlink(p);
+ __ptrace_detach(p, 0);
}
} while_each_thread(g,p);
write_unlock_irq(&tasklist_lock);
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index 9d5cd10..0d36750 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -84,6 +84,7 @@
extern int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len);
extern int ptrace_attach(struct task_struct *tsk);
extern int ptrace_detach(struct task_struct *, unsigned int);
+extern void __ptrace_detach(struct task_struct *, unsigned int);
extern void ptrace_disable(struct task_struct *);
extern int ptrace_check_attach(struct task_struct *task, int kill);
extern int ptrace_request(struct task_struct *child, long request, long addr, long data);
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index d2cf144..d95a72c 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -72,8 +72,8 @@
*/
void __ptrace_unlink(task_t *child)
{
- if (!child->ptrace)
- BUG();
+ BUG_ON(!child->ptrace);
+
child->ptrace = 0;
if (!list_empty(&child->ptrace_list)) {
list_del_init(&child->ptrace_list);
@@ -184,22 +184,27 @@
return retval;
}
-int ptrace_detach(struct task_struct *child, unsigned int data)
+void __ptrace_detach(struct task_struct *child, unsigned int data)
{
- if (!valid_signal(data))
- return -EIO;
-
- /* Architecture-specific hardware disable .. */
- ptrace_disable(child);
-
- /* .. re-parent .. */
child->exit_code = data;
-
- write_lock_irq(&tasklist_lock);
+ /* .. re-parent .. */
__ptrace_unlink(child);
/* .. and wake it up. */
if (child->exit_state != EXIT_ZOMBIE)
wake_up_process(child);
+}
+
+int ptrace_detach(struct task_struct *child, unsigned int data)
+{
+ if (!valid_signal(data))
+ return -EIO;
+
+ /* Architecture-specific hardware disable .. */
+ ptrace_disable(child);
+
+ write_lock_irq(&tasklist_lock);
+ if (child->ptrace)
+ __ptrace_detach(child, data);
write_unlock_irq(&tasklist_lock);
return 0;