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Date: Mon, 19 Nov 2007 12:31:59 +0300 From: Pavel Emelyanov <xemul@...nvz.org> To: Oleg Nesterov <oleg@...sign.ru>, Andrew Morton <akpm@...ux-foundation.org> CC: "Eric W. Biederman" <ebiederm@...ssion.com>, Pavel Emelyanov <xemul@...nvz.org>, linux-kernel@...r.kernel.org Subject: Re: [PATCH] do_task_stat: don't use task_pid_nr_ns() lockless Oleg Nesterov wrote: > Without rcu/tasklist/siglock lock task_pid_nr_ns() may read the freed memory, > move the callsite under ->siglock. > > Sadly, we can report pid == 0 if the task was detached. > > Signed-off-by: Oleg Nesterov <oleg@...sign.ru> Acked-by: Pavel Emelyanov <xemul@...nvz.org> > --- 24/fs/proc/array.c~dtst 2007-11-09 12:57:30.000000000 +0300 > +++ 24/fs/proc/array.c 2007-11-17 21:26:55.000000000 +0300 > @@ -392,7 +392,7 @@ static int do_task_stat(struct task_stru > sigset_t sigign, sigcatch; > char state; > int res; > - pid_t ppid = 0, pgid = -1, sid = -1; > + pid_t pid = 0, ppid = 0, pgid = -1, sid = -1; > int num_threads = 0; > struct mm_struct *mm; > unsigned long long start_time; > @@ -403,9 +403,6 @@ static int do_task_stat(struct task_stru > unsigned long rsslim = 0; > char tcomm[sizeof(task->comm)]; > unsigned long flags; > - struct pid_namespace *ns; > - > - ns = current->nsproxy->pid_ns; > > state = *get_task_state(task); > vsize = eip = esp = 0; > @@ -425,6 +422,7 @@ static int do_task_stat(struct task_stru > > rcu_read_lock(); > if (lock_task_sighand(task, &flags)) { > + struct pid_namespace *ns = current->nsproxy->pid_ns; > struct signal_struct *sig = task->signal; > > if (sig->tty) { > @@ -461,6 +459,7 @@ static int do_task_stat(struct task_stru > gtime = cputime_add(gtime, sig->gtime); > } > > + pid = task_pid_nr_ns(task, ns); > sid = task_session_nr_ns(task, ns); > pgid = task_pgrp_nr_ns(task, ns); > ppid = task_ppid_nr_ns(task, ns); > @@ -495,7 +494,7 @@ static int do_task_stat(struct task_stru > res = sprintf(buffer, "%d (%s) %c %d %d %d %d %d %u %lu \ > %lu %lu %lu %lu %lu %ld %ld %ld %ld %d 0 %llu %lu %ld %lu %lu %lu %lu %lu \ > %lu %lu %lu %lu %lu %lu %lu %lu %d %d %u %u %llu %lu %ld\n", > - task_pid_nr_ns(task, ns), > + pid, > tcomm, > state, > ppid, > > - 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/
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