Messages in this thread Patch in this message | | | Date | Sun, 31 May 2009 00:38:24 +0200 | From | Oleg Nesterov <> | Subject | [RFC PATCH 01/12 v3] ptrace: ptrace_signal: fix the usage of ->parent |
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This patch complicates the code to fix the pure theoretical problems. But since we are going to change this code, it is better to fix them anyway.
- If we are not traced any longer after ptrace_stop(), si_pid/si_uid are not necessary right.
- It is not safe to dereference current->parent without tasklist or RCU lock. The tracer can detach and exit. ->siglock can't prevent this, and (in theory) local_irq_disable() doesn't imply RCU lock.
Hopefully this "signr != info->si_signo" code will go away eventually.
Signed-off-by: Oleg Nesterov <oleg@redhat.com> ---
kernel/signal.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-)
--- PTRACE/kernel/signal.c~01_PTRACE_SIGNAL 2009-05-30 21:30:04.000000000 +0200 +++ PTRACE/kernel/signal.c 2009-05-30 21:52:00.000000000 +0200 @@ -1770,11 +1770,22 @@ static int ptrace_signal(int signr, sigi specific in the siginfo structure then it should have updated *info via PTRACE_SETSIGINFO. */ if (signr != info->si_signo) { + struct task_struct *tracer; + info->si_signo = signr; info->si_errno = 0; info->si_code = SI_USER; - info->si_pid = task_pid_vnr(current->parent); - info->si_uid = task_uid(current->parent); + + rcu_read_lock(); + tracer = current->parent; + if (task_ptrace(current)) { + info->si_pid = task_pid_vnr(tracer); + info->si_uid = task_uid(tracer); + } else { + info->si_pid = 0; + info->si_uid = 0; + } + rcu_read_unlock(); } /* If the (new) signal is now blocked, requeue it. */
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