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fix overread in Intra4Preds_NEON

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Extend VP8EncIterator::i4_boundary_ by 3 bytes to avoid Intra4Preds_NEON
reading deeper into the struct (likely padding) when top is positioned
at offset 29. This data is memset with MSan to prevent a warning due to
its incorrect modeling of tbl instructions.

Prior to:
  169dfbf9 disable Intra4Preds_NEON
there was a mismatch in the preprocessor checks for enabling the
function in NEON and removing the C version; NEON used `BPS == 32` while
the C code was removed unconditionally when building for aarch64. This
patch also normalizes those checks to look for `BPS == 32` and `BPS !=
32` as appropriate.

Bug: b:366668849,webp:372109644
Change-Id: Ic9e6ad4b2d844cb446decd63aec0b2676a89c8d0
This commit is contained in:
James Zern
2024-10-08 12:53:47 -07:00
parent 874069042e
commit 78ed683978
4 changed files with 22 additions and 10 deletions
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9
src/dsp/enc.c
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@ -359,8 +359,7 @@ static void Intra16Preds_C(uint8_t* WEBP_RESTRICT dst,
//------------------------------------------------------------------------------
// luma 4x4 prediction
// TODO: b/366668849 - Restore this condition after Intra4Preds_NEON is fixed.
#if 1 // !WEBP_NEON_OMIT_C_CODE || !WEBP_AARCH64
#if !WEBP_NEON_OMIT_C_CODE || !WEBP_AARCH64 || BPS != 32
#define DST(x, y) dst[(x) + (y) * BPS]
#define AVG3(a, b, c) ((uint8_t)(((a) + 2 * (b) + (c) + 2) >> 2))
@ -551,7 +550,7 @@ static void Intra4Preds_C(uint8_t* WEBP_RESTRICT dst,
HU4(I4HU4 + dst, top);
}
#endif // !WEBP_NEON_OMIT_C_CODE || !WEBP_AARCH64
#endif // !WEBP_NEON_OMIT_C_CODE || !WEBP_AARCH64 || BPS != 32
//------------------------------------------------------------------------------
// Metric
@ -798,9 +797,9 @@ WEBP_DSP_INIT_FUNC(VP8EncDspInit) {
VP8EncQuantizeBlockWHT = QuantizeBlock_C;
#endif
// TODO: b/366668849 - Move this into the #if after Intra4Preds_NEON is
// fixed.
#if !WEBP_NEON_OMIT_C_CODE || !WEBP_AARCH64 || BPS != 32
VP8EncPredLuma4 = Intra4Preds_C;
#endif
#if !WEBP_NEON_OMIT_C_CODE || !WEBP_AARCH64
VP8EncPredLuma16 = Intra16Preds_C;
#endif