Please consider the attached patch.

Before: "Overread buffer. Invalid header?" despite that all bytes are 
there (the precheck is wrong, not the parsing after the precheck)
After: transcoding is fine

A (zeroed) sample file is available at https://trac.ffmpeg.org/ticket/10259

Jérôme

On 19/10/2022 11:47, Jerome Martinez wrote:
> stride value is not relevant with unpadded content and the total count 
> of pixels (width x height) must be used instead of the rounding based 
> on width only then multiplied by height
>
> unpadded_10bit value computing is moved sooner in the code in order to 
> be able to use it during computing of minimal content size
>
> Fix 'Overread buffer' error when the content is not lucky enough to 
> have (enough) padding bytes at the end for not being rejected by the 
> formula based on the stride value
>
> Signed-off-by: Jerome Martinez <jerome@mediaarea.net>
> ---
>  libavcodec/dpx.c | 34 ++++++++++++++++++----------------
>  1 file changed, 18 insertions(+), 16 deletions(-)
>
> diff --git a/libavcodec/dpx.c b/libavcodec/dpx.c
> index 4f50608..d4699f6 100644
> --- a/libavcodec/dpx.c
> +++ b/libavcodec/dpx.c
> @@ -476,14 +476,30 @@ static int decode_frame(AVCodecContext *avctx, 
> AVFrame *p,
>          avctx->colorspace = AVCOL_SPC_RGB;
>      }
>
> +    av_strlcpy(creator, avpkt->data + 160, 100);
> +    creator[100] = '\0';
> +    av_dict_set(&p->metadata, "Creator", creator, 0);
> +
> +    av_strlcpy(input_device, avpkt->data + 1556, 32);
> +    input_device[32] = '\0';
> +    av_dict_set(&p->metadata, "Input Device", input_device, 0);
> +
> +    // Some devices do not pad 10bit samples to whole 32bit words per 
> row
> +    if (!memcmp(input_device, "Scanity", 7) ||
> +        !memcmp(creator, "Lasergraphics Inc.", 18)) {
> +        unpadded_10bit = 1;
> +    }
> +
>      // Table 3c: Runs will always break at scan line boundaries. Packing
>      // will always break to the next 32-bit word at scan-line 
> boundaries.
>      // Unfortunately, the encoder produced invalid files, so attempt
>      // to detect it
> +    // Also handle special case with unpadded content
>      need_align = FFALIGN(stride, 4);
> -    if (need_align*avctx->height + (int64_t)offset > avpkt->size) {
> +    if (need_align*avctx->height + (int64_t)offset > avpkt->size &&
> +        (!unpadded_10bit || (avctx->width * avctx->height * elements 
> + 2) / 3 * 4 + (int64_t)offset > avpkt->size)) {
>          // Alignment seems unappliable, try without
> -        if (stride*avctx->height + (int64_t)offset > avpkt->size) {
> +        if (stride*avctx->height + (int64_t)offset > avpkt->size || 
> unpadded_10bit) {
>              av_log(avctx, AV_LOG_ERROR, "Overread buffer. Invalid 
> header?\n");
>              return AVERROR_INVALIDDATA;
>          } else {
> @@ -609,20 +625,6 @@ static int decode_frame(AVCodecContext *avctx, 
> AVFrame *p,
>      if ((ret = ff_get_buffer(avctx, p, 0)) < 0)
>          return ret;
>
> -    av_strlcpy(creator, avpkt->data + 160, 100);
> -    creator[100] = '\0';
> -    av_dict_set(&p->metadata, "Creator", creator, 0);
> -
> -    av_strlcpy(input_device, avpkt->data + 1556, 32);
> -    input_device[32] = '\0';
> -    av_dict_set(&p->metadata, "Input Device", input_device, 0);
> -
> -    // Some devices do not pad 10bit samples to whole 32bit words per 
> row
> -    if (!memcmp(input_device, "Scanity", 7) ||
> -        !memcmp(creator, "Lasergraphics Inc.", 18)) {
> -        unpadded_10bit = 1;
> -    }
> -
>      // Move pointer to offset from start of file
>      buf =  avpkt->data + offset;
>