lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Message-ID: <20071117181549.GA1415@tv-sign.ru>
Date:	Sat, 17 Nov 2007 21:15:49 +0300
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Pavel Emelyanov <xemul@...nvz.org>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] task_pid_nr_ns() breaks proc_pid_readdir()

proc_pid_readdir:

	for (...; ...; task = next_tgid(tgid + 1, ns)) {
		tgid = task_pid_nr_ns(task, ns);
		... use tgid ...

The first problem is that task_pid_nr_ns() can race with RCU and read the
freed memory.

However, rcu_read_lock() can't help. next_tgid() returns a pinned task_struct,
but the task can be released (and it's pid detached) before task_pid_nr_ns()
reads the pid_t value. In that case task_pid_nr_ns() returns 0 thus breaking
the whole logic.

Make sure that task_pid_nr_ns() returns !0 before updating tgid. Note that
next_tgid(tgid + 1) can find the same "struct pid" again, but we shouldn't
go into the endless loop because pid_task(PIDTYPE_PID) must return NULL in
this case, so next_tgid() can't return the same task.

Signed-off-by: Oleg Nesterov <oleg@...sign.ru>

--- 24/fs/proc/base.c~pprd	2007-10-25 16:22:11.000000000 +0400
+++ 24/fs/proc/base.c	2007-11-17 20:58:14.000000000 +0300
@@ -2481,7 +2481,15 @@ int proc_pid_readdir(struct file * filp,
 	for (task = next_tgid(tgid, ns);
 	     task;
 	     put_task_struct(task), task = next_tgid(tgid + 1, ns)) {
-		tgid = task_pid_nr_ns(task, ns);
+		int nr;
+
+		rcu_read_lock();
+		nr = task_pid_nr_ns(task, ns);
+		rcu_read_unlock();
+		if (!nr)
+			continue;
+
+		tgid = nr;
 		filp->f_pos = tgid + TGID_OFFSET;
 		if (proc_pid_fill_cache(filp, dirent, filldir, task, tgid) < 0) {
 			put_task_struct(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

Powered by Openwall GNU/*/Linux Powered by OpenVZ