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[91.9.80.211]) by smtp.googlemail.com with ESMTPSA id d17sm54076863wjr.14.2016.11.26.14.36.49 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 26 Nov 2016 14:36:50 -0800 (PST) From: Andreas Cadhalpun X-Google-Original-From: Andreas Cadhalpun To: ffmpeg-devel@ffmpeg.org References: <20161126005343.GA4824@nb4> Message-ID: <285a0213-2a77-fa4c-4412-e1f296423e14@googlemail.com> Date: Sat, 26 Nov 2016 23:36:48 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Icedove/45.4.0 MIME-Version: 1.0 In-Reply-To: <20161126005343.GA4824@nb4> Subject: Re: [FFmpeg-devel] [PATCH] pngdec: check if previous frame exists instead of trusting sequence_number 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 Errors-To: ffmpeg-devel-bounces@ffmpeg.org Sender: "ffmpeg-devel" On 26.11.2016 01:53, Michael Niedermayer wrote: > On Fri, Nov 25, 2016 at 10:13:06PM +0100, Andreas Cadhalpun wrote: >> This fixes a segmentation fault caused by calling memcpy with NULL as >> second argument in handle_p_frame_apng. >> >> Signed-off-by: Andreas Cadhalpun >> --- >> libavcodec/pngdec.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/libavcodec/pngdec.c b/libavcodec/pngdec.c >> index 36275ae..a7b330b 100644 >> --- a/libavcodec/pngdec.c >> +++ b/libavcodec/pngdec.c >> @@ -922,7 +922,7 @@ static int decode_fctl_chunk(AVCodecContext *avctx, PNGDecContext *s, >> return AVERROR_INVALIDDATA; >> } >> >> - if (sequence_number == 0 && dispose_op == APNG_DISPOSE_OP_PREVIOUS) { >> + if (!s->previous_picture.f->data[0] && dispose_op == APNG_DISPOSE_OP_PREVIOUS) { >> // No previous frame to revert to for the first frame >> // Spec says to just treat it as a APNG_DISPOSE_OP_BACKGROUND >> dispose_op = APNG_DISPOSE_OP_BACKGROUND; > > wont this be different when seeking back to the > first frame ? > is that intended ? I don't think the apng demuxer supports seeking. But it shouldn't hurt to check both sequence_number and the previous frame. Updated patch is attached. Best regards, Andreas From 84125e5f32fd4b9146d9926d2f8a4467da7c8557 Mon Sep 17 00:00:00 2001 From: Andreas Cadhalpun Date: Fri, 25 Nov 2016 22:09:51 +0100 Subject: [PATCH] pngdec: check if previous frame exists instead of trusting sequence_number This fixes a segmentation fault caused by calling memcpy with NULL as second argument in handle_p_frame_apng. Signed-off-by: Andreas Cadhalpun --- libavcodec/pngdec.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/libavcodec/pngdec.c b/libavcodec/pngdec.c index 36275ae..2f8d266 100644 --- a/libavcodec/pngdec.c +++ b/libavcodec/pngdec.c @@ -922,7 +922,8 @@ static int decode_fctl_chunk(AVCodecContext *avctx, PNGDecContext *s, return AVERROR_INVALIDDATA; } - if (sequence_number == 0 && dispose_op == APNG_DISPOSE_OP_PREVIOUS) { + if ((sequence_number == 0 || !s->previous_picture.f->data[0]) && + dispose_op == APNG_DISPOSE_OP_PREVIOUS) { // No previous frame to revert to for the first frame // Spec says to just treat it as a APNG_DISPOSE_OP_BACKGROUND dispose_op = APNG_DISPOSE_OP_BACKGROUND; -- 2.10.2