[FFmpeg-devel] [PATCH v1 2/3] avcodec/jpeg2000dec: add support for HTJ2K block decoding

[Michael Niedermayer]

On Sun, Apr 02, 2023 at 03:21:08PM -0700, Pierre-Anthony Lemieux wrote:
> On Sun, Apr 2, 2023 at 3:17 PM Michael Niedermayer
> <michael at niedermayer.cc> wrote:
> >
> > On Fri, Mar 31, 2023 at 08:29:40AM -0700, pal at sandflow.com wrote:
> > > From: caleb <etemesicaleb at gmail.com>
[...]
> > [...]
> > > +/**
> > > + * Drops bits from lower bits in the bit buffer. buf contains the bit buffers.
> > > + * nbits is the number of bits to remove.
> > > + */
> > > +av_always_inline
> > > +static void jpeg2000_bitbuf_drop_bits_lsb(StateVars *buf, uint8_t nbits)
> > > +{
> > > +    if (buf->bits_left < nbits) {
> >
> > > +        av_log(NULL, AV_LOG_ERROR, "Invalid bit read of %d, bits in buffer are %d\n", nbits, buf->bits_left);
> > > +        av_assert0(0);
> >
> >
> > [...]
> > > +int
> > > +ff_jpeg2000_decode_htj2k(const Jpeg2000DecoderContext *s, Jpeg2000CodingStyle *codsty, Jpeg2000T1Context *t1, Jpeg2000Cblk *cblk,
> > > +                         int width, int height, int magp, uint8_t roi_shift)
> > > +{
> > > +    uint8_t p0 = 0;             // Number of placeholder passes
> > > +    uint32_t Lcup;              // Length of HT cleanup segment
> > > +    uint32_t Lref;              // Length of Refinement segment
> > > +    uint32_t Scup;              // HT cleanup segment suffix length
> > > +    uint32_t Pcup;              // HT cleanup segment prefix length
> > > +
> > > +    uint8_t S_blk;              // Number of skipped magnitude bitplanes
> > > +    uint8_t pLSB;
> > > +
> > > +    uint8_t *Dcup;              // Byte of an HT cleanup segment
> > > +    uint8_t *Dref;              // Byte of an HT refinement segment
> > > +
> > > +    int z_blk;                  // Number of ht coding pass
> > > +
> > > +    uint8_t empty_passes;
> > > +
> > > +    StateVars mag_sgn;          // Magnitude and Sign
> > > +    StateVars mel;              // Adaptive run-length coding
> > > +    StateVars vlc;              // Variable Length coding
> > > +    StateVars sig_prop;         // Significance propagation
> > > +
> > > +    MelDecoderState mel_state;
> > > +
> > > +    int ret;
> > > +
> > > +    /* Temporary buffers */
> > > +    int32_t *sample_buf;
> > > +    uint8_t *block_states;
> > > +
> > > +    int32_t n, val;             // Post-processing
> > > +
> > > +    int32_t M_b = magp;
> > > +    av_assert0(width <= 1024U && height <= 1024U);
> > > +    av_assert0(width * height <= 4096);
> > > +    av_assert0(width * height > 0);
> >
> > Has this decoder been tested with some fuzzer ?
> 
> Yes.

ok


> 
> > I see a bunch of asserts in it and i dont immedeatly see what would prevent them from
> > triggering

maybe you can add comments to the asserts that explain why these are
guranteed to be true

thx

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

Modern terrorism, a quick summary: Need oil, start war with country that
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people, be surprised about them taking revenge and drop even more bombs
and strip your own citizens of their rights and freedoms. to be continued
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