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[PATCH] fix zap_thread's ptrace related problems

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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>
This commit is contained in:
Oleg Nesterov 2006-02-15 22:50:10 +03:00 committed by Linus Torvalds
parent dadac81b1b
commit 5ecfbae093
3 changed files with 19 additions and 13 deletions
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2
fs/exec.c
View file

@ -1403,7 +1403,7 @@ static void zap_threads (struct mm_struct *mm)
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);

1
include/linux/ptrace.h
View file

@ -84,6 +84,7 @@ extern int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __us
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);

29
kernel/ptrace.c
View file

@ -72,8 +72,8 @@ void ptrace_untrace(task_t *child)
*/
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 @@ bad:
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;