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gh-96821: Fix undefined behaviour in `audioop.c` (#96923) · python/cpython@553d3c1 · GitHub
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matthiasgoergensblurb-it[bot]
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gh-96821: Fix undefined behaviour in audioop.c (#96923)
* gh-96821: Fix undefined behaviour in `audioop.c` Left-shifting negative numbers is undefined behaviour. Fortunately, multiplication works just as well, is defined behaviour, and gets compiled to the same machine code as before by optimizing compilers. Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
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Lines changed: 16 additions & 12 deletions

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‎Misc/NEWS.d/next/Core and Builtins/2022-09-19-03-35-01.gh-issue-96821.izK6JA.rst‎

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Fix undefined behaviour in ``audioop.c``.

‎Modules/audioop.c‎

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@@ -59,6 +59,8 @@ static const int16_t seg_uend[8] = {
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static int16_t
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search(int16_t val, const int16_t *table, int size)
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{
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assert(0 <= size);
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assert(size < INT16_MAX);
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int i;
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for (i = 0; i < size; i++) {
@@ -170,6 +172,7 @@ st_14linear2ulaw(int16_t pcm_val) /* 2's complement (14-bit range) */
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if (seg >= 8) /* out of range, return maximum value. */
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return (unsigned char) (0x7F ^ mask);
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else {
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assert(seg >= 0);
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uval = (unsigned char) (seg << 4) | ((pcm_val >> (seg + 1)) & 0xF);
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return (uval ^ mask);
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}
@@ -300,13 +303,13 @@ static const int stepsizeTable[89] = {
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#ifdef WORDS_BIGENDIAN
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#define GETINT24(cp, i) ( \
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((unsigned char *)(cp) + (i))[2] + \
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(((unsigned char *)(cp) + (i))[1] << 8) + \
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(((signed char *)(cp) + (i))[0] << 16) )
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(((unsigned char *)(cp) + (i))[1] * (1 << 8)) + \
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(((signed char *)(cp) + (i))[0] * (1 << 16)) )
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#else
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#define GETINT24(cp, i) ( \
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((unsigned char *)(cp) + (i))[0] + \
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(((unsigned char *)(cp) + (i))[1] << 8) + \
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(((signed char *)(cp) + (i))[2] << 16) )
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(((unsigned char *)(cp) + (i))[1] * (1 << 8)) + \
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(((signed char *)(cp) + (i))[2] * (1 << 16)) )
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#endif
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@@ -347,10 +350,10 @@ static const int stepsizeTable[89] = {
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} while(0)
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#define GETSAMPLE32(size, cp, i) ( \
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(size == 1) ? (int)GETINT8((cp), (i)) << 24 : \
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(size == 2) ? (int)GETINT16((cp), (i)) << 16 : \
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(size == 3) ? (int)GETINT24((cp), (i)) << 8 : \
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#define GETSAMPLE32(size, cp, i) ( \
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(size == 1) ? (int)GETINT8((cp), (i)) * (1 << 24) : \
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(size == 2) ? (int)GETINT16((cp), (i)) * (1 << 16) : \
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(size == 3) ? (int)GETINT24((cp), (i)) * (1 << 8) : \
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(int)GETINT32((cp), (i)))
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#define SETSAMPLE32(size, cp, i, val) do { \
@@ -1558,7 +1561,7 @@ audioop_ulaw2lin_impl(PyObject *module, Py_buffer *fragment, int width)
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cp = fragment->buf;
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for (i = 0; i < fragment->len*width; i += width) {
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int val = st_ulaw2linear16(*cp++) << 16;
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int val = st_ulaw2linear16(*cp++) * (1 << 16);
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SETSAMPLE32(width, ncp, i, val);
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}
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return rv;
@@ -1632,7 +1635,7 @@ audioop_alaw2lin_impl(PyObject *module, Py_buffer *fragment, int width)
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cp = fragment->buf;
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for (i = 0; i < fragment->len*width; i += width) {
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val = st_alaw2linear16(*cp++) << 16;
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val = st_alaw2linear16(*cp++) * (1 << 16);
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SETSAMPLE32(width, ncp, i, val);
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}
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return rv;
@@ -1757,7 +1760,7 @@ audioop_lin2adpcm_impl(PyObject *module, Py_buffer *fragment, int width,
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/* Step 6 - Output value */
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if ( bufferstep ) {
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outputbuffer = (delta << 4) & 0xf0;
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outputbuffer = (delta * (1 << 4)) & 0xf0;
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} else {
17621765
*ncp++ = (delta & 0x0f) | outputbuffer;
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}
@@ -1875,7 +1878,7 @@ audioop_adpcm2lin_impl(PyObject *module, Py_buffer *fragment, int width,
18751878
step = stepsizeTable[index];
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/* Step 6 - Output value */
1878-
SETSAMPLE32(width, ncp, i, valpred << 16);
1881+
SETSAMPLE32(width, ncp, i, valpred * (1 << 16));
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}
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rv = Py_BuildValue("(O(ii))", str, valpred, index);

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