[FFmpeg-devel] [PATCH] avcodec/exr detect invalid line offset table and recreate table

[Dzung Hoang]

Thanks Martin for your comments. I made the requested changes here.

--- libavcodec/exr.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+)
diff --git a/libavcodec/exr.c b/libavcodec/exr.cindex 034920f..265d44d 100644--- a/libavcodec/exr.c+++ b/libavcodec/exr.c@@ -1640,6 +1640,9 @@ static int decode_frame(AVCodecContext *avctx, void *data,     int out_line_size;     int nb_blocks;/* nb scanline or nb tile */
+    uint64_t *table;/* scanline offset table */+    uint8_t *marker;/* used to recreate invalid scanline offset table */+     bytestream2_init(&s->gb, avpkt->data, avpkt->size);
     if ((ret = decode_header(s, picture)) < 0)@@ -1731,6 +1734,21 @@ static int decode_frame(AVCodecContext *avctx, void *data,     s->buf_size = avpkt->size;     ptr         = picture->data[0];
+    // check offset table+    if (!s->is_tile && bytestream2_peek_le64(&s->gb) == 0)+    {+        table = (uint64_t *)s->gb.buffer;+        marker = avpkt->data + bytestream2_tell(&s->gb) + nb_blocks * 8;++        av_log(s->avctx, AV_LOG_DEBUG, "recreating invalid scanline offset table\n");++        for (y = 0; y < nb_blocks; y++)+        {+            table[y] = marker - s->buf;+            marker += ((uint32_t *)marker)[1] + 8;+        }+    }+     // Zero out the start if ymin is not 0     for (y = 0; y < s->ymin; y++) {         memset(ptr, 0, out_line_size);--2.1.4



      From: Martin Vignali <martin.vignali at gmail.com>
 To: FFmpeg development discussions and patches <ffmpeg-devel at ffmpeg.org> 
 Sent: Saturday, March 18, 2017 7:14 AM
 Subject: Re: [FFmpeg-devel] [PATCH] avcodec/exr detect invalid line offset table and recreate table
   
Hello,

I tested your patch on mac, seems to work, and doesn't break exr fate test.

Some comments :


> ---
>  libavcodec/exr.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
>
> diff --git a/libavcodec/exr.c b/libavcodec/exr.c
> index 034920f..dec21af 100644
> --- a/libavcodec/exr.c
> +++ b/libavcodec/exr.c
> @@ -1726,6 +1726,25 @@ static int decode_frame(AVCodecContext *avctx, void
> *data,
>    if (bytestream2_get_bytes_left(&s->gb) < nb_blocks * 8)
>        return AVERROR_INVALIDDATA;
>
> +    // check line offset table and recreate if first entry is 0
> +    if (bytestream2_peek_le64(&s->gb) == 0)
> +    {
>
You should probably test if the file is in scanline (using s->is_tile).
After taking a quick look to the official library, this table
reconstruction seems to be only for scanline picture.


> +        uint64_t *table = (uint64_t *)s->gb.buffer;
> +        uint8_t *head = avpkt->data;
> +        uint8_t *marker = head + bytestream2_tell(&s->gb) + nb_blocks * 8;
>

You should probably move variable declaration to the top of the function.


> +
> +        av_log(s->avctx, AV_LOG_INFO, "Recreating invalid offset
> table.\n");
> +
> +        // recreate the line offset table using the length field for each
> line
> +        // decode_block() will check for out-of-bounds offsets, so do not
> bother
> +        // to check here
> +        for (y = 0; y < nb_blocks; y++)
> +        {
> +            table[y] = marker - head;
> +            marker += ((uint32_t *)marker)[1] + 8;
> +        }
> +    }
> +
>
>
    // save pointer we are going to use in decode_block
>    s->buf      = avpkt->data;
>    s->buf_size = avpkt->size;
> --
>

You should also add a fate test for a short sample.


Martin
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