[FFmpeg-devel] [PATCH] lavc/golomb: Fix UE golomb overwrite issue.

[Michael Niedermayer]

On Fri, May 26, 2017 at 09:19:09AM +0800, Jun Zhao wrote:
>  golomb.h |    5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 228c7180856b65d095dd0b8d59f3d3ff4f65774a  0001-lavc-golomb-Fix-UE-golomb-overwrite-issue.patch
> From eabcbf3d41e83f24623e6195d4a0ff86e4d95a80 Mon Sep 17 00:00:00 2001
> From: Jun Zhao <jun.zhao at intel.com>
> Date: Fri, 26 May 2017 09:02:29 +0800
> Subject: [PATCH] lavc/golomb: Fix UE golomb overwrite issue.
> 
> put_bits just support write up to 31 bits, when write 32 bit in
> put_bits, it's will overwrite the bit buffer, because the default
> assert level is 0, the av_assert2(n <= 31 && value < (1U << n))
> in put_bits can not be trigger runtime.
> 
> Signed-off-by: Jun Zhao <jun.zhao at intel.com>
> ---
>  libavcodec/golomb.h | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/libavcodec/golomb.h b/libavcodec/golomb.h
> index 0833aff468..2c5a969ac1 100644
> --- a/libavcodec/golomb.h
> +++ b/libavcodec/golomb.h
> @@ -468,7 +468,10 @@ static inline void set_ue_golomb(PutBitContext *pb, int i)
>          put_bits(pb, ff_ue_golomb_len[i], i + 1);
>      else {
>          int e = av_log2(i + 1);
> -        put_bits(pb, 2 * e + 1, i + 1);
> +        if (e < 16)
> +            put_bits(pb, 2 * e + 1, i + 1);
> +        else
> +            put_bits32(pb, i + 1);

this is wrong

if e is 16 or larger the length is 33 bits or longer its never
32

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

it is not once nor twice but times without number that the same ideas make
their appearance in the world. -- Aristotle
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