Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756594AbaFXQEd (ORCPT ); Tue, 24 Jun 2014 12:04:33 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:33344 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754232AbaFXP4V (ORCPT ); Tue, 24 Jun 2014 11:56:21 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Johan Hovold Subject: [PATCH 3.15 27/61] USB: cdc-acm: fix write and resume race Date: Tue, 24 Jun 2014 11:51:10 -0400 Message-Id: <20140624154954.009828597@linuxfoundation.org> X-Mailer: git-send-email 2.0.0 In-Reply-To: <20140624154952.751713761@linuxfoundation.org> References: <20140624154952.751713761@linuxfoundation.org> User-Agent: quilt/0.63-1 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Johan Hovold commit e144ed28bed10684f9aaec6325ed974d53f76110 upstream. Fix race between write() and resume() due to improper locking that could lead to writes being reordered. Resume must be done atomically and susp_count be protected by the write_lock in order to prevent racing with write(). This could otherwise lead to writes being reordered if write() grabs the write_lock after susp_count is decremented, but before the delayed urb is submitted. Fixes: 11ea859d64b6 ("USB: additional power savings for cdc-acm devices that support remote wakeup") Signed-off-by: Johan Hovold Signed-off-by: Greg Kroah-Hartman --- drivers/usb/class/cdc-acm.c | 23 +++++++++-------------- 1 file changed, 9 insertions(+), 14 deletions(-) --- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -1541,27 +1541,20 @@ static int acm_resume(struct usb_interfa struct acm *acm = usb_get_intfdata(intf); struct acm_wb *wb; int rv = 0; - int cnt; spin_lock_irq(&acm->read_lock); - acm->susp_count -= 1; - cnt = acm->susp_count; - spin_unlock_irq(&acm->read_lock); + spin_lock(&acm->write_lock); - if (cnt) - return 0; + if (--acm->susp_count) + goto out; if (test_bit(ASYNCB_INITIALIZED, &acm->port.flags)) { - rv = usb_submit_urb(acm->ctrlurb, GFP_NOIO); + rv = usb_submit_urb(acm->ctrlurb, GFP_ATOMIC); - spin_lock_irq(&acm->write_lock); if (acm->delayed_wb) { wb = acm->delayed_wb; acm->delayed_wb = NULL; - spin_unlock_irq(&acm->write_lock); acm_start_wb(acm, wb); - } else { - spin_unlock_irq(&acm->write_lock); } /* @@ -1569,12 +1562,14 @@ static int acm_resume(struct usb_interfa * do the write path at all cost */ if (rv < 0) - goto err_out; + goto out; - rv = acm_submit_read_urbs(acm, GFP_NOIO); + rv = acm_submit_read_urbs(acm, GFP_ATOMIC); } +out: + spin_unlock(&acm->write_lock); + spin_unlock_irq(&acm->read_lock); -err_out: return rv; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/