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Add SHL32_ovflw() and use it in IMDCT

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Prevents integer overflow UB in the headroom left shift when
the signal blows up on bad bitstreams (if it triggers, the
signal was already unusable anyway).
This commit is contained in:
Jean-Marc Valin 2025-04-03 14:45:24 -04:00
parent a013aa0477
commit 60b8f5b803
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GPG key ID: 8D2952BBB52C646D
4 changed files with 7 additions and 2 deletions
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1
celt/arch.h
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@ -330,6 +330,7 @@ static OPUS_INLINE int celt_isnan(float x)
#define SUB32(a,b) ((a)-(b))
#define ADD32_ovflw(a,b) ((a)+(b))
#define SUB32_ovflw(a,b) ((a)-(b))
#define SHL32_ovflw(a,shift) (a)
#define PSHR32_ovflw(a,shift) (a)
#define MULT16_16_16(a,b) ((a)*(b))

2
celt/fixed_debug.h
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@ -69,6 +69,8 @@ extern opus_int64 celt_mips;
/* Avoid MSVC warning C4146: unary minus operator applied to unsigned type */
/** Negate 32-bit value, ignore any overflows */
#define NEG32_ovflw(a) (celt_mips+=2,(opus_val32)(0-(opus_uint32)(a)))
/** 32-bit shift left, ignoring overflows */
#define SHL32_ovflw(a,shift) ((opus_int32)((opus_uint32)(a)<<(shift)))
/** 32-bit arithmetic shift right with rounding-to-nearest, ignoring overflows */
#define PSHR32_ovflw(a,shift) (SHR32(ADD32_ovflw(a, (EXTEND32(1)<<(shift)>>1)),shift))

2
celt/fixed_generic.h
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@ -147,6 +147,8 @@
/* Avoid MSVC warning C4146: unary minus operator applied to unsigned type */
/** Negate 32-bit value, ignore any overflows */
#define NEG32_ovflw(a) ((opus_val32)(0-(opus_uint32)(a)))
/** 32-bit shift left, ignoring overflows */
#define SHL32_ovflw(a,shift) SHL32(a,shift)
/** 32-bit arithmetic shift right with rounding-to-nearest, ignoring overflows */
#define PSHR32_ovflw(a,shift) (SHR32(ADD32_ovflw(a, (EXTEND32(1)<<(shift)>>1)),shift))

4
celt/mdct.c
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@ -297,8 +297,8 @@ void clt_mdct_backward_c(const mdct_lookup *l, kiss_fft_scalar *in, kiss_fft_sca
kiss_fft_scalar yr, yi;
opus_val32 x1, x2;
rev = *bitrev++;
x1 = SHL32(*xp1, IMDCT_HEADROOM);
x2 = SHL32(*xp2, IMDCT_HEADROOM);
x1 = SHL32_ovflw(*xp1, IMDCT_HEADROOM);
x2 = SHL32_ovflw(*xp2, IMDCT_HEADROOM);
yr = ADD32_ovflw(S_MUL(x2, t[i]), S_MUL(x1, t[N4+i]));
yi = SUB32_ovflw(S_MUL(x1, t[i]), S_MUL(x2, t[N4+i]));
/* We swap real and imag because we use an FFT instead of an IFFT. */