[FFmpeg-devel] avcodec/alsdec: Consider frame_size in ra_block handling

Submitted by Michael Niedermayer on June 20, 2019, 2:17 p.m.

Details

Message ID 20190620141710.32418-1-michael@niedermayer.cc
State New
Headers show

Commit Message

Michael Niedermayer June 20, 2019, 2:17 p.m.
Fixes: out of array access
Fixes: 15277/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ALS_fuzzer-5184853437317120

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
 libavcodec/alsdec.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

Comments

Thilo Borgmann June 20, 2019, 4:06 p.m.
Am 20.06.19 um 16:17 schrieb Michael Niedermayer:
> Fixes: out of array access
> Fixes: 15277/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ALS_fuzzer-5184853437317120
> 
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>  libavcodec/alsdec.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/libavcodec/alsdec.c b/libavcodec/alsdec.c
> index e50a287f19..f94086efcb 100644
> --- a/libavcodec/alsdec.c
> +++ b/libavcodec/alsdec.c
> @@ -789,14 +789,15 @@ static int read_var_block_data(ALSDecContext *ctx, ALSBlockData *bd)
>  
>      // read first value and residuals in case of a random access block
>      if (bd->ra_block) {
> -        if (opt_order)

pls add a comment here like:

// limit possibly corrupted opt_order

and push if tested.

> +        int len = FFMIN(opt_order, sconf->frame_length);
> +        if (len)
>              bd->raw_samples[0] = decode_rice(gb, avctx->bits_per_raw_sample - 4);
> -        if (opt_order > 1)
> +        if (len > 1)
>              bd->raw_samples[1] = decode_rice(gb, FFMIN(s[0] + 3, ctx->s_max));
> -        if (opt_order > 2)
> +        if (len > 2)
>              bd->raw_samples[2] = decode_rice(gb, FFMIN(s[0] + 1, ctx->s_max));
>  
> -        start = FFMIN(opt_order, 3);
> +        start = FFMIN(len, 3);
>      }
>  
>      // read all residuals
> 

-Thilo
Michael Niedermayer June 20, 2019, 4:13 p.m.
On Thu, Jun 20, 2019 at 06:06:29PM +0200, Thilo Borgmann wrote:
> Am 20.06.19 um 16:17 schrieb Michael Niedermayer:
> > Fixes: out of array access
> > Fixes: 15277/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ALS_fuzzer-5184853437317120
> > 
> > Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> > Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> > ---
> >  libavcodec/alsdec.c | 9 +++++----
> >  1 file changed, 5 insertions(+), 4 deletions(-)
> > 
> > diff --git a/libavcodec/alsdec.c b/libavcodec/alsdec.c
> > index e50a287f19..f94086efcb 100644
> > --- a/libavcodec/alsdec.c
> > +++ b/libavcodec/alsdec.c
> > @@ -789,14 +789,15 @@ static int read_var_block_data(ALSDecContext *ctx, ALSBlockData *bd)
> >  
> >      // read first value and residuals in case of a random access block
> >      if (bd->ra_block) {
> > -        if (opt_order)
> 
> pls add a comment here like:
> 
> // limit possibly corrupted opt_order

will do


> 
> and push if tested.

yes it fixes this issue but there are more related issues, ill
post a patch that should fix all.

thx

[...]

Patch hide | download patch | download mbox

diff --git a/libavcodec/alsdec.c b/libavcodec/alsdec.c
index e50a287f19..f94086efcb 100644
--- a/libavcodec/alsdec.c
+++ b/libavcodec/alsdec.c
@@ -789,14 +789,15 @@  static int read_var_block_data(ALSDecContext *ctx, ALSBlockData *bd)
 
     // read first value and residuals in case of a random access block
     if (bd->ra_block) {
-        if (opt_order)
+        int len = FFMIN(opt_order, sconf->frame_length);
+        if (len)
             bd->raw_samples[0] = decode_rice(gb, avctx->bits_per_raw_sample - 4);
-        if (opt_order > 1)
+        if (len > 1)
             bd->raw_samples[1] = decode_rice(gb, FFMIN(s[0] + 3, ctx->s_max));
-        if (opt_order > 2)
+        if (len > 2)
             bd->raw_samples[2] = decode_rice(gb, FFMIN(s[0] + 1, ctx->s_max));
 
-        start = FFMIN(opt_order, 3);
+        start = FFMIN(len, 3);
     }
 
     // read all residuals