linux-kernel - [PATCH] pid_ns: ensure pid is not freed during kill_pid_info_as

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Date:	Mon, 26 Sep 2011 10:18:29 -0500
From:	Serge Hallyn <serge.hallyn@...onical.com>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	"Serge E. Hallyn" <serge@...lyn.com>, Greg KH <greg@...ah.com>,
	Oleg Nesterov <oleg@...hat.com>,
	lkml <linux-kernel@...r.kernel.org>, richard@....at,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Tejun Heo <tj@...nel.org>, linux-usb@...r.kernel.org,
	"Serge E. Hallyn" <serge.hallyn@...onical.com>
Subject: [PATCH] pid_ns: ensure pid is not freed during kill_pid_info_as_uid

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.

Signed-off-by: Serge Hallyn <serge.hallyn@...onical.com>
---
 drivers/usb/core/devio.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index 37518df..eea53eb 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -407,7 +407,7 @@ 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;
@@ -422,9 +422,11 @@ 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);
 }
-- 
1.7.0.4

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