From 169dfbf9310808b9cbd05662f7bfee97f5e86582 Mon Sep 17 00:00:00 2001
From: James Zern <jzern@google.com>
Date: Wed, 2 Oct 2024 15:23:03 -0700
Subject: [PATCH] disable Intra4Preds_NEON

The load of the `top` parameter may over read causing MSan errors:

==7373==WARNING: MemorySanitizer: use-of-uninitialized-value
  #0 0xfff891d52ad4 in Intra4Preds_NEON src/dsp/enc_neon.c:1003:12
  #1 0xfff892d87618 in MakeIntra4Preds src/enc/quant_enc.c:484:3

Bug: b:366668849
Change-Id: I29cf3b2f402ee79ea93c1ee2a4fdd95083aeed68
---
 src/dsp/enc.c      | 7 +++++--
 src/dsp/enc_neon.c | 6 +++++-
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/src/dsp/enc.c b/src/dsp/enc.c
index cb44ba6f..1d1aac59 100644
--- a/src/dsp/enc.c
+++ b/src/dsp/enc.c
@@ -345,7 +345,8 @@ static void Intra16Preds_C(uint8_t* dst,
 //------------------------------------------------------------------------------
 // luma 4x4 prediction
 
-#if !WEBP_NEON_OMIT_C_CODE || !WEBP_AARCH64
+// TODO: b/366668849 - Restore this condition after Intra4Preds_NEON is fixed.
+#if 1  // !WEBP_NEON_OMIT_C_CODE || !WEBP_AARCH64
 
 #define DST(x, y) dst[(x) + (y) * BPS]
 #define AVG3(a, b, c) ((uint8_t)(((a) + 2 * (b) + (c) + 2) >> 2))
@@ -769,8 +770,10 @@ WEBP_DSP_INIT_FUNC(VP8EncDspInit) {
   VP8EncQuantizeBlockWHT = QuantizeBlock_C;
 #endif
 
-#if !WEBP_NEON_OMIT_C_CODE || !WEBP_AARCH64
+  // TODO: b/366668849 - Move this into the #if after Intra4Preds_NEON is
+  // fixed.
   VP8EncPredLuma4 = Intra4Preds_C;
+#if !WEBP_NEON_OMIT_C_CODE || !WEBP_AARCH64
   VP8EncPredLuma16 = Intra16Preds_C;
 #endif
 
diff --git a/src/dsp/enc_neon.c b/src/dsp/enc_neon.c
index 7ba5b2d6..5b88c07e 100644
--- a/src/dsp/enc_neon.c
+++ b/src/dsp/enc_neon.c
@@ -913,6 +913,8 @@ static int Quantize2Blocks_NEON(int16_t in[32], int16_t out[32],
 
 #if WEBP_AARCH64
 
+// TODO: b/366668849 - enable Intra4Preds_NEON after fixing overread.
+#if 0
 #define DC4_VE4_HE4_TM4_NEON(dst, tbl, res, lane)                              \
   do {                                                                         \
     uint8x16_t r;                                                              \
@@ -1023,6 +1025,7 @@ static void Intra4Preds_NEON(uint8_t* dst, const uint8_t* top) {
   vst1_u8(dst + I4HD4 + BPS * 2, vget_low_u8(result1));
   vst1_u8(dst + I4HD4 + BPS * 3, vget_high_u8(result1));
 }
+#endif  // 0
 
 static WEBP_INLINE void Fill_NEON(uint8_t* dst, const uint8_t value) {
   uint8x16_t a = vdupq_n_u8(value);
@@ -1193,7 +1196,8 @@ WEBP_TSAN_IGNORE_FUNCTION void VP8EncDspInitNEON(void) {
   VP8SSE4x4 = SSE4x4_NEON;
 
 #if WEBP_AARCH64
-#if BPS == 32
+  // TODO: b/366668849 - enable Intra4Preds_NEON after fixing overread.
+#if 0  // BPS == 32
   VP8EncPredLuma4 = Intra4Preds_NEON;
 #endif
   VP8EncPredLuma16 = Intra16Preds_NEON;