[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Date: Wed, 6 May 2009 00:47:22 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Chris Wright <chrisw@...s-sol.org>,
Roland McGrath <roland@...hat.com>,
linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] ptrace: ptrace_attach: check PF_KTHREAD + exit_state
instead of ->mm
- Add PF_KTHREAD check to prevent attaching to the kernel thread
with a borrowed ->mm.
With or without this change we can race with daemonize() which
can set PF_KTHREAD or clear ->mm after ptrace_attach() does the
check, but this doesn't matter because reparent_to_kthreadd()
does ptrace_unlink().
- Kill "!task->mm" check. We don't really care about ->mm != NULL,
and the task can call exit_mm() right after we drop task_lock().
What we need is to make sure we can't attach after exit_notify(),
check task->exit_state != 0 instead.
Also, move the "already traced" check down for cosmetic reasons.
Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
kernel/ptrace.c | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)
--- PTRACE/kernel/ptrace.c~1_KTHREADS 2009-05-05 21:37:26.000000000 +0200
+++ PTRACE/kernel/ptrace.c 2009-05-05 23:17:53.000000000 +0200
@@ -182,6 +182,8 @@ int ptrace_attach(struct task_struct *ta
audit_ptrace(task);
retval = -EPERM;
+ if (unlikely(task->flags & PF_KTHREAD))
+ goto out;
if (same_thread_group(task, current))
goto out;
@@ -191,8 +193,6 @@ int ptrace_attach(struct task_struct *ta
retval = mutex_lock_interruptible(&task->cred_exec_mutex);
if (retval < 0)
goto out;
-
- retval = -EPERM;
repeat:
/*
* Nasty, nasty.
@@ -212,23 +212,24 @@ repeat:
goto repeat;
}
- if (!task->mm)
- goto bad;
- /* the same process cannot be attached many times */
- if (task->ptrace & PT_PTRACED)
- goto bad;
retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH);
if (retval)
goto bad;
- /* Go */
+ retval = -EPERM;
+ if (unlikely(task->exit_state))
+ goto bad;
+ if (task->ptrace & PT_PTRACED)
+ goto bad;
+
task->ptrace |= PT_PTRACED;
if (capable(CAP_SYS_PTRACE))
task->ptrace |= PT_PTRACE_CAP;
__ptrace_link(task, current);
-
send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);
+
+ retval = 0;
bad:
write_unlock_irqrestore(&tasklist_lock, flags);
task_unlock(task);
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists