[FFmpeg-devel] [PATCH] avcodec/tiff: Check order only for tags that we process

[Mathias Koehler via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

The initial out of order check was introduced with commit
ad29f9e47cb avcodec/tiff: Restrict tag order based on specification

This changes the check to only check against tags the we process
since tags that we don't process shouldn't cause any bugs.

Example of CinemaDNG files with incorrect ordered tags
that causes problems: https://www.dji.com/de/inspire-3/samples
---
 libavcodec/tiff.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/libavcodec/tiff.c b/libavcodec/tiff.c
index bb8120bc1b..7458167fb3 100644
--- a/libavcodec/tiff.c
+++ b/libavcodec/tiff.c
@@ -1254,7 +1254,7 @@ static int tiff_decode_tag(TiffContext *s, AVFrame *frame)
 {
     AVFrameSideData *sd;
     GetByteContext gb_temp;
-    unsigned tag, type, count, off, value = 0, value2 = 1; // value2 is a denominator so init. to 1
+    unsigned tag, prev_last_tag, type, count, off, value = 0, value2 = 1; // value2 is a denominator so init. to 1
     int i, start;
     int pos;
     int ret;
@@ -1268,8 +1268,10 @@ static int tiff_decode_tag(TiffContext *s, AVFrame *frame)
         return AVERROR_INVALIDDATA;
 
     // We ignore TIFF_STRIP_SIZE as it is sometimes in the logic but wrong order around TIFF_STRIP_OFFS
-    if (tag != TIFF_STRIP_SIZE)
+    if (tag != TIFF_STRIP_SIZE) {
+        prev_last_tag = s->last_tag;
         s->last_tag = tag;
+    }
 
     off = bytestream2_tell(&s->gb);
     if (count == 1) {
@@ -1874,6 +1876,8 @@ static int tiff_decode_tag(TiffContext *s, AVFrame *frame)
         tiff_set_type(s, TIFF_TYPE_CINEMADNG);
         break;
     default:
+        // We don't care about out of order tags that we don't process
+        s->last_tag = prev_last_tag;
         if (s->avctx->err_recognition & AV_EF_EXPLODE) {
             av_log(s->avctx, AV_LOG_ERROR,
                    "Unknown or unsupported tag %d/0x%0X\n",
-- 
2.51.0

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