linux-kernel - [061/107] USB: pid_ns: ensure pid is not freed during kill_pid_info_as

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Date:	Wed, 02 Nov 2011 15:14:27 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Serge Hallyn <serge.hallyn@...onical.com>
Subject: [061/107] USB: pid_ns: ensure pid is not freed during kill_pid_info_as_uid

2.6.32-longterm review patch.  If anyone has any objections, please let us know.

------------------

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

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>

---
 drivers/usb/core/devio.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -403,7 +403,7 @@ static void async_completed(struct 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;
@@ -416,9 +416,11 @@ static void async_completed(struct 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);
 }


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