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

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

[Mathias Koehler via ffmpeg-devel]

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

_______________________________________________
ffmpeg-devel mailing list -- ffmpeg-devel@ffmpeg.org
To unsubscribe send an email to ffmpeg-devel-leave@ffmpeg.org

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

[Michael Niedermayer via ffmpeg-devel]

[-- Attachment #1.1: Type: text/plain, Size: 1230 bytes --]

Hi Mathias

On Wed, Nov 05, 2025 at 12:29:53PM +0100, Mathias Koehler via ffmpeg-devel wrote:
> 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(-)

what tags are that ?
any "user" tags that can be more cleanly excluded ?

I dont like this patch because its not really leading itself to a
clean implementation when more exceptions appear

I think its better to define in a clean, terse and general way the ordering
our decoder can handle. Something that works with all tags not just ones we
skip

thx

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The real ebay dictionary, page 2
"100% positive feedback" - "All either got their money back or didnt complain"
"Best seller ever, very honest" - "Seller refunded buyer after failed scam"

[-- Attachment #1.2: signature.asc --]
[-- Type: application/pgp-signature, Size: 195 bytes --]

[-- Attachment #2: Type: text/plain, Size: 163 bytes --]

_______________________________________________
ffmpeg-devel mailing list -- ffmpeg-devel@ffmpeg.org
To unsubscribe send an email to ffmpeg-devel-leave@ffmpeg.org