From patchwork Sun Jun 23 23:42:31 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andreas Rheinhardt X-Patchwork-Id: 13686 Return-Path: X-Original-To: patchwork@ffaux-bg.ffmpeg.org Delivered-To: patchwork@ffaux-bg.ffmpeg.org Received: from ffbox0-bg.mplayerhq.hu (ffbox0-bg.ffmpeg.org [79.124.17.100]) by ffaux.localdomain (Postfix) with ESMTP id CD0CF448B31 for ; Mon, 24 Jun 2019 02:43:57 +0300 (EEST) Received: from [127.0.1.1] (localhost [127.0.0.1]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTP id B9A6468AAC3; Mon, 24 Jun 2019 02:43:57 +0300 (EEST) X-Original-To: ffmpeg-devel@ffmpeg.org Delivered-To: ffmpeg-devel@ffmpeg.org Received: from mail-wr1-f67.google.com (mail-wr1-f67.google.com [209.85.221.67]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTPS id EBA736898F6 for ; Mon, 24 Jun 2019 02:43:51 +0300 (EEST) Received: by mail-wr1-f67.google.com with SMTP id v14so11905610wrr.4 for ; Sun, 23 Jun 2019 16:43:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=NYkdO/t2HLuXczyluMEKQhHjMR0vmctsZJOckPkgiDc=; b=HSSptQVPl9vn13O2iUfLKlMQpPaIMSB+wRc09pbqdp/CPV682qqcTV62kU6fsgn/yI sB1KhM4Zu52UFBXyHxjXNFXQVTJonPWjltWOlWVgN8GzW3+T2+6h+b1co7lLTOtioRB9 +rYCTKqGFVvOZSxXe21M6xzKYW9IRPC+lkxgwu3cZDb3t30I+V9mRfmxVHcc30HzZt78 zMC31bd4yFbEaq9hz7gR8uTpdg7kMrrOER38IcmaKtGlew7z1589aaB5UMXqV2LrujAH hAJEVSGGSzCTnWIPUjiRlgOEkA/oAyqUlrS8tvzLnjxtBT6YPymLSuDH2boM8xwleK6e O9uA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=NYkdO/t2HLuXczyluMEKQhHjMR0vmctsZJOckPkgiDc=; b=aZbHBVHhebZ7sk95h9wR0DGLcH9vIg1Ygy6esVeo/Lql/1qHnTUut8SMcCoC+FUfwA 3bBjzYocV984fj8vpThVfrxU2BhiIk5fIJtCS+tgKS6RrXlFyFJvETUKiuTPEpDe5RlJ h34LHOdqNejiIZ6mNC37GXvfO6j5nfeXu4HSDeHQOIGNmVZygxUjZ8HEK8sL5pllBUWC lGCZmfIrWqrtBI88/p952FrjSJAMUXpQmQcpQ6MYnQ58N9H7yixqCl5yZbixHiWHTH4P b+ga6Tv9IRZFu2o8IVcPvbwPSI3bhqZclkjiC0VchhsWm0uMELSUfM2L4dsEP1c2lrjx ih1g== X-Gm-Message-State: APjAAAV05rco6Ld/k/W3Y1lcP3r5QoO13mNrZB1jiQuwZPrqovoBkoZ1 8oIycZ4YTxHXrobuShvTkuspQhr3 X-Google-Smtp-Source: APXvYqz13lkq6HOykPxRyIRTtj1KJ7I3T0NIUz609m8DbJnVix0GyuSvKd5oDQMtO4pkR1PJvpELeQ== X-Received: by 2002:adf:f186:: with SMTP id h6mr16106096wro.274.1561333431373; Sun, 23 Jun 2019 16:43:51 -0700 (PDT) Received: from localhost.localdomain (ipbcc063db.dynamic.kabel-deutschland.de. [188.192.99.219]) by smtp.gmail.com with ESMTPSA id b6sm7087102wrx.85.2019.06.23.16.43.50 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Sun, 23 Jun 2019 16:43:50 -0700 (PDT) From: Andreas Rheinhardt To: ffmpeg-devel@ffmpeg.org Date: Mon, 24 Jun 2019 01:42:31 +0200 Message-Id: <20190623234231.6348-3-andreas.rheinhardt@gmail.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190623234231.6348-1-andreas.rheinhardt@gmail.com> References: <2b14f7af-4e9a-bebd-43f5-c2b5c761c915@gmail.com> <20190623234231.6348-1-andreas.rheinhardt@gmail.com> MIME-Version: 1.0 Subject: [FFmpeg-devel] [PATCH 13/13] avformat/matroskadec: Improve error/EOF checks III X-BeenThere: ffmpeg-devel@ffmpeg.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: FFmpeg development discussions and patches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: FFmpeg development discussions and patches Cc: Andreas Rheinhardt Errors-To: ffmpeg-devel-bounces@ffmpeg.org Sender: "ffmpeg-devel" Up until now, when an element was skipped, it was relied upon ffio_limit to make sure that there is enough data available to skip. ffio_limit itself relies upon the availability of the file's size. As this needn't be available, the check has been refined: First one byte less than intended is skipped, then another byte is read, followed by a check of the error flags. Signed-off-by: Andreas Rheinhardt --- libavformat/matroskadec.c | 24 +++++++++++++++++------- 1 file changed, 17 insertions(+), 7 deletions(-) diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c index 1db7471440..caabfcf6ac 100644 --- a/libavformat/matroskadec.c +++ b/libavformat/matroskadec.c @@ -1256,13 +1256,23 @@ static int ebml_parse_elem(MatroskaDemuxContext *matroska, case EBML_STOP: return 1; default: - if (ffio_limit(pb, length) != length) { - // ffio_limit emits its own error message, - // so we don't have to. - return AVERROR(EIO); - } - res = avio_skip(pb, length); - res = res < 0 ? res : 0; + if (length) { + if (ffio_limit(pb, length) != length) { + // ffio_limit emits its own error message, + // so we don't have to. + return AVERROR(EIO); + } + if ((res = avio_skip(pb, length - 1)) >= 0) { + // avio_skip might take us past EOF. We check for this + // by skipping only length - 1 bytes, reading a byte and + // checking the error flags. This is done in order to check + // that the element has been properly skipped even when + // no filesize (that ffio_limit relies on) is available. + avio_r8(pb); + res = NEEDS_CHECKING; + } + } else + res = 0; } if (res) { if (res == NEEDS_CHECKING) {