From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D2D1EC677D4 for ; Mon, 8 Oct 2018 18:36:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9130E21479 for ; Mon, 8 Oct 2018 18:36:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="SYaSUC92" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9130E21479 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728443AbeJIBtC (ORCPT ); Mon, 8 Oct 2018 21:49:02 -0400 Received: from mail.kernel.org ([198.145.29.99]:33578 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726522AbeJIBtB (ORCPT ); Mon, 8 Oct 2018 21:49:01 -0400 Received: from localhost (ip-213-127-77-176.ip.prioritytelecom.net [213.127.77.176]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 5C2CD20C0A; Mon, 8 Oct 2018 18:35:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1539023758; bh=VSkDEurWOOXpIThIU5L1vF9LuLHcJHp6pTpmmdgtLDw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SYaSUC92RIvxe/SZueDBpAiT3K//7lAnbrQaadts1NL/VWlyh9SCYuYJ9WXeD/NrD LT6I8KnRCl/r+W0aFikHcVXPzFS63zYs9Vf+Jw/paEk1YGT8KsMq0zoZJNCgzD8qid yXciMDX12jlNU997377hg3UZ47YC+YtN0sIjMMto= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Sakari Ailus , Hans Verkuil , Laurent Pinchart , Mauro Carvalho Chehab Subject: [PATCH 4.4 073/113] media: v4l: event: Prevent freeing event subscriptions while accessed Date: Mon, 8 Oct 2018 20:31:14 +0200 Message-Id: <20181008175534.969849501@linuxfoundation.org> X-Mailer: git-send-email 2.19.0 In-Reply-To: <20181008175530.864641368@linuxfoundation.org> References: <20181008175530.864641368@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Sakari Ailus commit ad608fbcf166fec809e402d548761768f602702c upstream. The event subscriptions are added to the subscribed event list while holding a spinlock, but that lock is subsequently released while still accessing the subscription object. This makes it possible to unsubscribe the event --- and freeing the subscription object's memory --- while the subscription object is simultaneously accessed. Prevent this by adding a mutex to serialise the event subscription and unsubscription. This also gives a guarantee to the callback ops that the add op has returned before the del op is called. This change also results in making the elems field less special: subscriptions are only added to the event list once they are fully initialised. Signed-off-by: Sakari Ailus Reviewed-by: Hans Verkuil Reviewed-by: Laurent Pinchart Cc: stable@vger.kernel.org # for 4.14 and up Fixes: c3b5b0241f62 ("V4L/DVB: V4L: Events: Add backend") Signed-off-by: Mauro Carvalho Chehab Signed-off-by: Greg Kroah-Hartman --- drivers/media/v4l2-core/v4l2-event.c | 37 +++++++++++++++++------------------ drivers/media/v4l2-core/v4l2-fh.c | 2 + include/media/v4l2-fh.h | 1 3 files changed, 22 insertions(+), 18 deletions(-) --- a/drivers/media/v4l2-core/v4l2-event.c +++ b/drivers/media/v4l2-core/v4l2-event.c @@ -119,14 +119,6 @@ static void __v4l2_event_queue_fh(struct if (sev == NULL) return; - /* - * If the event has been added to the fh->subscribed list, but its - * add op has not completed yet elems will be 0, treat this as - * not being subscribed. - */ - if (!sev->elems) - return; - /* Increase event sequence number on fh. */ fh->sequence++; @@ -212,6 +204,7 @@ int v4l2_event_subscribe(struct v4l2_fh struct v4l2_subscribed_event *sev, *found_ev; unsigned long flags; unsigned i; + int ret = 0; if (sub->type == V4L2_EVENT_ALL) return -EINVAL; @@ -229,31 +222,36 @@ int v4l2_event_subscribe(struct v4l2_fh sev->flags = sub->flags; sev->fh = fh; sev->ops = ops; + sev->elems = elems; + + mutex_lock(&fh->subscribe_lock); spin_lock_irqsave(&fh->vdev->fh_lock, flags); found_ev = v4l2_event_subscribed(fh, sub->type, sub->id); - if (!found_ev) - list_add(&sev->list, &fh->subscribed); spin_unlock_irqrestore(&fh->vdev->fh_lock, flags); if (found_ev) { + /* Already listening */ kfree(sev); - return 0; /* Already listening */ + goto out_unlock; } if (sev->ops && sev->ops->add) { - int ret = sev->ops->add(sev, elems); + ret = sev->ops->add(sev, elems); if (ret) { - sev->ops = NULL; - v4l2_event_unsubscribe(fh, sub); - return ret; + kfree(sev); + goto out_unlock; } } - /* Mark as ready for use */ - sev->elems = elems; + spin_lock_irqsave(&fh->vdev->fh_lock, flags); + list_add(&sev->list, &fh->subscribed); + spin_unlock_irqrestore(&fh->vdev->fh_lock, flags); - return 0; +out_unlock: + mutex_unlock(&fh->subscribe_lock); + + return ret; } EXPORT_SYMBOL_GPL(v4l2_event_subscribe); @@ -292,6 +290,8 @@ int v4l2_event_unsubscribe(struct v4l2_f return 0; } + mutex_lock(&fh->subscribe_lock); + spin_lock_irqsave(&fh->vdev->fh_lock, flags); sev = v4l2_event_subscribed(fh, sub->type, sub->id); @@ -310,6 +310,7 @@ int v4l2_event_unsubscribe(struct v4l2_f sev->ops->del(sev); kfree(sev); + mutex_unlock(&fh->subscribe_lock); return 0; } --- a/drivers/media/v4l2-core/v4l2-fh.c +++ b/drivers/media/v4l2-core/v4l2-fh.c @@ -49,6 +49,7 @@ void v4l2_fh_init(struct v4l2_fh *fh, st INIT_LIST_HEAD(&fh->available); INIT_LIST_HEAD(&fh->subscribed); fh->sequence = -1; + mutex_init(&fh->subscribe_lock); } EXPORT_SYMBOL_GPL(v4l2_fh_init); @@ -93,6 +94,7 @@ void v4l2_fh_exit(struct v4l2_fh *fh) if (fh->vdev == NULL) return; v4l2_event_unsubscribe_all(fh); + mutex_destroy(&fh->subscribe_lock); fh->vdev = NULL; } EXPORT_SYMBOL_GPL(v4l2_fh_exit); --- a/include/media/v4l2-fh.h +++ b/include/media/v4l2-fh.h @@ -43,6 +43,7 @@ struct v4l2_fh { wait_queue_head_t wait; struct list_head subscribed; /* Subscribed events */ struct list_head available; /* Dequeueable event */ + struct mutex subscribe_lock; unsigned int navailable; u32 sequence;