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,URIBL_BLOCKED autolearn=unavailable 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 A08D8C433E8 for ; Fri, 24 Jul 2020 20:00:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 42D522070B for ; Fri, 24 Jul 2020 20:00:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=yandex.ru header.i=@yandex.ru header.b="MgU8A3bl" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726783AbgGXUAL (ORCPT ); Fri, 24 Jul 2020 16:00:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42610 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726562AbgGXUAK (ORCPT ); Fri, 24 Jul 2020 16:00:10 -0400 Received: from forward501j.mail.yandex.net (forward501j.mail.yandex.net [IPv6:2a02:6b8:0:801:2::111]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0F467C0619D3 for ; Fri, 24 Jul 2020 13:00:10 -0700 (PDT) Received: from mxback5q.mail.yandex.net (mxback5q.mail.yandex.net [IPv6:2a02:6b8:c0e:1ba:0:640:b716:ad89]) by forward501j.mail.yandex.net (Yandex) with ESMTP id C307F33801CB; Fri, 24 Jul 2020 23:00:06 +0300 (MSK) Received: from localhost (localhost [::1]) by mxback5q.mail.yandex.net (mxback/Yandex) with ESMTP id 5G8zRixIVZ-06OCbMfU; Fri, 24 Jul 2020 23:00:06 +0300 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yandex.ru; s=mail; t=1595620806; bh=f93LtYxJ50+Ck2fwWUZ066AeOsoEDLCakGsqNBbVsmc=; h=Message-Id:Cc:Subject:In-Reply-To:Date:References:To:From; b=MgU8A3bl60LibhWwfqSDep/IguW6d8QdhmcCphQmzUSjdnd27j4At9yE0l81yK40f fr8xEFwxpkY5IZwde85G+DgPN4QHnaxK8u3+dPnEjlaO6tR0Lkw0Cz3uNqmhyokK/8 pZUvTgrVddFV7HLDKZW9ttxsyqLiT2V+jZwcyMTk= Authentication-Results: mxback5q.mail.yandex.net; dkim=pass header.i=@yandex.ru Received: by vla5-344e18ef0bef.qloud-c.yandex.net with HTTP; Fri, 24 Jul 2020 23:00:06 +0300 From: Evgeny Novikov Envelope-From: eugenenovikov@yandex.ru To: "Lad, Prabhakar" Cc: Mauro Carvalho Chehab , linux-media , LKML , "ldv-project@linuxtesting.org" In-Reply-To: References: <20200723170453.432-1-novikov@ispras.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: Fri, 24 Jul 2020 23:00:06 +0300 Message-Id: <20927111595619342@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, 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()! 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). --  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