[FFmpeg-devel] [PATCH 1/2] avcodec/dvbsubenc: Use 64bits in nb_colors and num_rects checks

[FFmpeg-devel] [PATCH 1/2] avcodec/dvbsubenc: Use 64bits in nb_colors and num_rects checks

[Michael Niedermayer]

Fixes: integer overflow

No testcase

Found-by: 김승호 <kimsho98@naver.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
 libavcodec/dvbsubenc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libavcodec/dvbsubenc.c b/libavcodec/dvbsubenc.c
index 822e3a53099..53f0f6412fa 100644
--- a/libavcodec/dvbsubenc.c
+++ b/libavcodec/dvbsubenc.c
@@ -302,7 +302,7 @@ static int dvbsub_encode(AVCodecContext *avctx, uint8_t *outbuf, int buf_size,
 
     /* page composition segment */
 
-    if (buf_size < 8 + h->num_rects * 6)
+    if (buf_size < 8 + h->num_rects * 6LL)
         return AVERROR_BUFFER_TOO_SMALL;
     *q++ = 0x0f; /* sync_byte */
     *q++ = 0x10; /* segment_type */
@@ -326,7 +326,7 @@ static int dvbsub_encode(AVCodecContext *avctx, uint8_t *outbuf, int buf_size,
 
     if (h->num_rects) {
         for (clut_id = 0; clut_id < h->num_rects; clut_id++) {
-            if (buf_size < 6 + h->rects[clut_id]->nb_colors * 6)
+            if (buf_size < 6 + h->rects[clut_id]->nb_colors * 6LL)
                 return AVERROR_BUFFER_TOO_SMALL;
 
             /* CLUT segment */
-- 
2.49.0

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[FFmpeg-devel] [PATCH 2/2] avcodec/encode: Check nb_colors

[Michael Niedermayer]

Fixes: integer overflow

No testcase

Found-by: 김승호 <kimsho98@naver.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
 libavcodec/encode.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/libavcodec/encode.c b/libavcodec/encode.c
index 72dfa8867ab..6a7781336f2 100644
--- a/libavcodec/encode.c
+++ b/libavcodec/encode.c
@@ -197,6 +197,12 @@ int avcodec_encode_subtitle(AVCodecContext *avctx, uint8_t *buf, int buf_size,
         return -1;
     }
 
+    for (int i = 0; i<sub->num_rects; i++)
+        if (sub->rects[i]->nb_colors > 256) {
+            av_log(avctx, AV_LOG_ERROR, "nb_colors %d in rect %d is too large\n", sub->rects[i]->nb_colors, i);
+            return AVERROR_PATCHWELCOME;
+        }
+
     ret = ffcodec(avctx->codec)->cb.encode_sub(avctx, buf, buf_size, sub);
     avctx->frame_num++;
     return ret;
-- 
2.49.0

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Re: [FFmpeg-devel] [PATCH 1/2] avcodec/dvbsubenc: Use 64bits in nb_colors and num_rects checks

[Andreas Rheinhardt]

Michael Niedermayer:
> Fixes: integer overflow
> 
> No testcase
> 
> Found-by: 김승호 <kimsho98@naver.com>
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>  libavcodec/dvbsubenc.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/libavcodec/dvbsubenc.c b/libavcodec/dvbsubenc.c
> index 822e3a53099..53f0f6412fa 100644
> --- a/libavcodec/dvbsubenc.c
> +++ b/libavcodec/dvbsubenc.c
> @@ -302,7 +302,7 @@ static int dvbsub_encode(AVCodecContext *avctx, uint8_t *outbuf, int buf_size,
>  
>      /* page composition segment */
>  
> -    if (buf_size < 8 + h->num_rects * 6)
> +    if (buf_size < 8 + h->num_rects * 6LL)
>          return AVERROR_BUFFER_TOO_SMALL;
>      *q++ = 0x0f; /* sync_byte */
>      *q++ = 0x10; /* segment_type */
> @@ -326,7 +326,7 @@ static int dvbsub_encode(AVCodecContext *avctx, uint8_t *outbuf, int buf_size,
>  
>      if (h->num_rects) {
>          for (clut_id = 0; clut_id < h->num_rects; clut_id++) {
> -            if (buf_size < 6 + h->rects[clut_id]->nb_colors * 6)
> +            if (buf_size < 6 + h->rects[clut_id]->nb_colors * 6LL)
>                  return AVERROR_BUFFER_TOO_SMALL;
>  
>              /* CLUT segment */

I just sent different patches for this:
https://ffmpeg.org/pipermail/ffmpeg-devel/2025-April/342314.html
They are intended to make your patches obsolete.

- Andreas

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