[FFmpeg-devel] Re: [PR] lavc/aacdec_usac: fix CPE channel index in ff_aac_usac_reset_state() (PR #21469)

[Kieran Kunhya via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

On Wed, 14 Jan 2026, 18:22 ruikai via ffmpeg-devel, <ffmpeg-devel@ffmpeg.org>
wrote:

> PR #21469 opened by ruikai
> URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21469
> Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21469.patch
>
> fix a simple index bug in ff_aac_usac_reset_state()
> that writes past the end of ChannelElement.ch[2] for CPE
>
> ff_aac_usac_reset_state() loops over channels with j < ch, but
> incorrectly takes &che->ch[ch]. For CPE (ch == 2) this becomes
> che->ch[2], which is one past the end of ChannelElement.ch[2], and the
> subsequent memset() causes an intra-object out-of-bounds write.
>
> index the channel element with the loop variable (j).
>
>
> >From c8b8c41a6b2a3de017aaacb4cdc076cbd2cb8754 Mon Sep 17 00:00:00 2001
> From: Ruikai Peng <ruikai@pwno.io>
> Date: Wed, 14 Jan 2026 19:16:43 -0500
> Subject: [PATCH] lavc/aacdec_usac: fix CPE channel index in
>  ff_aac_usac_reset_state()
>
> fix a simple index bug in ff_aac_usac_reset_state()
> that writes past the end of ChannelElement.ch[2] for CPE
>
> ff_aac_usac_reset_state() loops over channels with j < ch, but
> incorrectly takes &che->ch[ch]. For CPE (ch == 2) this becomes
> che->ch[2], which is one past the end of ChannelElement.ch[2], and the
> subsequent memset() causes an intra-object out-of-bounds write.
>
> index the channel element with the loop variable (j).
> ---
>  libavcodec/aac/aacdec_usac.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/libavcodec/aac/aacdec_usac.c b/libavcodec/aac/aacdec_usac.c
> index c4b821bbba..237a247d5b 100644
> --- a/libavcodec/aac/aacdec_usac.c
> +++ b/libavcodec/aac/aacdec_usac.c
> @@ -315,7 +315,7 @@ int ff_aac_usac_reset_state(AACDecContext *ac,
> OutputConfiguration *oc)
>                  ff_aac_sbr_config_usac(ac, che, e);
>
>              for (int j = 0; j < ch; j++) {
> -                SingleChannelElement *sce = &che->ch[ch];
> +                SingleChannelElement *sce = &che->ch[j];
>                  AACUsacElemData *ue = &sce->ue;
>
>                  memset(ue, 0, sizeof(*ue));
> --
> 2.49.1
>
> _______________________________________________
> ffmpeg-devel mailing list -- ffmpeg-devel@ffmpeg.org
> To unsubscribe send an email to ffmpeg-devel-leave@ffmpeg.org



LGTM

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