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=-10.0 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 9127EC433DF for ; Sun, 2 Aug 2020 18:38:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6EFB420738 for ; Sun, 2 Aug 2020 18:38:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=yandex.ru header.i=@yandex.ru header.b="o30OIc8l" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727014AbgHBSig (ORCPT ); Sun, 2 Aug 2020 14:38:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47680 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725910AbgHBSif (ORCPT ); Sun, 2 Aug 2020 14:38:35 -0400 Received: from forward500o.mail.yandex.net (forward500o.mail.yandex.net [IPv6:2a02:6b8:0:1a2d::610]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 39FFAC06174A; Sun, 2 Aug 2020 11:38:34 -0700 (PDT) Received: from mxback7o.mail.yandex.net (mxback7o.mail.yandex.net [IPv6:2a02:6b8:0:1a2d::21]) by forward500o.mail.yandex.net (Yandex) with ESMTP id 69E4460054; Sun, 2 Aug 2020 21:38:32 +0300 (MSK) Received: from localhost (localhost [::1]) by mxback7o.mail.yandex.net (mxback/Yandex) with ESMTP id ZYUtAIGnwd-cVDSDtTX; Sun, 02 Aug 2020 21:38:31 +0300 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yandex.ru; s=mail; t=1596393511; bh=9Xpoz3PFFbPffZdHaYnv+jiyMQH/CQukz3eO2Np1tvY=; h=Message-Id:Cc:Subject:Date:References:To:From; b=o30OIc8ljvbdNE8zTXLiQjS5DpI1OdstfFF8re7kjUpkeTWNeaCspMlH8EUwjmCmP a09+5ilYEYN8zazr7aK4mrzdfrOBTqvjjbWOrY3CNy1R8uO4DXEVnXiXe3eJAD9+u8 KQvtevP/SQuvV6QTyQutUyvEpdWU+0DeFiHskcTQ= Authentication-Results: mxback7o.mail.yandex.net; dkim=pass header.i=@yandex.ru Received: by myt1-5b550442eff4.qloud-c.yandex.net with HTTP; Sun, 02 Aug 2020 21:38:31 +0300 From: Evgeny Novikov Envelope-From: eugenenovikov@yandex.ru To: "Lad, Prabhakar" Cc: Mauro Carvalho Chehab , linux-media , LKML , "ldv-project@linuxtesting.org" References: <20200723170453.432-1-novikov@ispras.ru> <20927111595619342@mail.yandex.ru> Subject: Re: [PATCH] media: davinci: vpif_capture: fix potential double free MIME-Version: 1.0 X-Mailer: Yamail [ http://yandex.ru ] 5.0 Date: Sun, 02 Aug 2020 21:38:31 +0300 Message-Id: <220911596048246@mail.yandex.ru> Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=utf-8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Lad, 25.07.2020, 01:06, "Lad, Prabhakar" : > Hi Evgeny, > > On Fri, Jul 24, 2020 at 9:00 PM Evgeny Novikov wrote: >>  Hi Lad, >> >>  Yet again I can not demonstrate you a nice error trace corresponding to the bug fixed by the patch. Indeed, there is a branch in vpif_probe() that explicitly invokes vpif_probe_complete() and the patch targets the possible issue that can happen during this. >> >>  When I developed the patch I saw on vpif_display.ko. It looks very similar regarding things touched by the patch. In particular, it does not free vpif_obj.sd in its vpif_probe_complete(). But now I see that it does this in vpif_remove()! > > Makes sense. > >>  Do you think that vpif_capture.ko should do the same? If so, I guess that I should fix the patch appropriately since likely it just replaces one (very rare) bug with another one (on a typical execution path). > > Yes it should. vpif_remove() from vpif_capture.ko already both frees vpif_obj.sd and unregisters the V4L2 device. So, there is no need to fix the patch. BTW, other drivers, e.g. drivers/media/platform/renesas-ceu.c, do not clean up memory allocated by probe within v4l2_async_notifier_operations.complete as well. -- Best regards, Evgeny Novikov > Cheers, > --Prabhakar > >>  -- >>  Evgeny Novikov >>  Linux Verification Center, ISP RAS >>  http://linuxtesting.org >> >>  24.07.2020, 17:17, "Lad, Prabhakar" : >>  > Hi Evgeny, >>  > >>  > Thank you for the patch. >>  > >>  > On Thu, Jul 23, 2020 at 6:04 PM Evgeny Novikov wrote: >>  >> In case of errors vpif_probe_complete() releases memory for vpif_obj.sd >>  >> and unregisters the V4L2 device. But then this is done again by >>  >> vpif_probe() itself. The patch removes the cleaning from >>  >> vpif_probe_complete(). >>  >> >>  >> Found by Linux Driver Verification project (linuxtesting.org). >>  >> >>  >> Signed-off-by: Evgeny Novikov >>  >> --- >>  >> drivers/media/platform/davinci/vpif_capture.c | 2 -- >>  >> 1 file changed, 2 deletions(-) >>  >> >>  >> diff --git a/drivers/media/platform/davinci/vpif_capture.c b/drivers/media/platform/davinci/vpif_capture.c >>  >> index d9ec439faefa..72a0e94e2e21 100644 >>  >> --- a/drivers/media/platform/davinci/vpif_capture.c >>  >> +++ b/drivers/media/platform/davinci/vpif_capture.c >>  >> @@ -1482,8 +1482,6 @@ static int vpif_probe_complete(void) >>  >> /* Unregister video device */ >>  >> video_unregister_device(&ch->video_dev); >>  >> } >>  >> - kfree(vpif_obj.sd); >>  >> - v4l2_device_unregister(&vpif_obj.v4l2_dev); >>  > >>  > vpif_probe_complete() is a async callback and probe() should have >>  > already completed by then. >>  > >>  > Cheers, >>  > --Prabhakar >>  > >>  >> return err; >>  >> } >>  >> -- >>  >> 2.16.4