linux-kernel - [v2.6.34-stable 073/165] USB: pid_ns: ensure pid is not freed during kill_pid_info_as

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Message-ID: <1345060109-9187-74-git-send-email-paul.gortmaker@windriver.com>
Date:	Wed, 15 Aug 2012 15:46:57 -0400
From:	Paul Gortmaker <paul.gortmaker@...driver.com>
To:	<stable@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:	Serge Hallyn <serge.hallyn@...onical.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Paul Gortmaker <paul.gortmaker@...driver.com>
Subject: [v2.6.34-stable 073/165] USB: pid_ns: ensure pid is not freed during kill_pid_info_as_uid

From: Serge Hallyn <serge.hallyn@...onical.com>

                   -------------------
    This is a commit scheduled for the next v2.6.34 longterm release.
    http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git
    If you see a problem with using this for longterm, please comment.
                   -------------------

commit aec01c5895051849ed842dc5b8794017a7751f28 upstream.

Alan Stern points out that after spin_unlock(&ps->lock) there is no
guarantee that ps->pid won't be freed.  Since kill_pid_info_as_uid() is
called after the spin_unlock(), the pid passed to it must be pinned.

Reported-by: Alan Stern <stern@...land.harvard.edu>
Signed-off-by: Serge Hallyn <serge.hallyn@...onical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com>
---
 drivers/usb/core/devio.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index 6088192..85a4967 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -409,7 +409,7 @@ static void async_completed(struct urb *urb)
 		sinfo.si_errno = as->status;
 		sinfo.si_code = SI_ASYNCIO;
 		sinfo.si_addr = as->userurb;
-		pid = as->pid;
+		pid = get_pid(as->pid);
 		uid = as->uid;
 		euid = as->euid;
 		secid = as->secid;
@@ -424,9 +424,11 @@ static void async_completed(struct urb *urb)
 		cancel_bulk_urbs(ps, as->bulk_addr);
 	spin_unlock(&ps->lock);
 
-	if (signr)
+	if (signr) {
 		kill_pid_info_as_uid(sinfo.si_signo, &sinfo, pid, uid,
 				      euid, secid);
+		put_pid(pid);
+	}
 
 	wake_up(&ps->wait);
 }
-- 
1.7.12.rc2

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