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FIX: Fixed out of bounds memory access #89

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FIX: Fixed out of bounds memory access #89

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38 changes: 23 additions & 15 deletions src/ffts_trig.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1063,7 +1063,15 @@ ffts_generate_table_1d_real_32f(struct _ffts_plan_t *const p,
hs = FFTS_ASSUME_ALIGNED_16(&half_secant[2 * offset]);

/* initialize from lookup table */
for (i = 0; i <= log_2; i++) {
/**
* Here a lookup only up to log2-1 is necessary, because in the iteration holds:
* i_log_2 < ffts_ctzl(N/4)
* -> i_log_2 < ffts_ctzl(N) - 2
* -> i_log_2 < log_2 - 2.
* The largest access to w is in w[i_log_2 +1], which is equivalent to
* w[log_2 -1], so we only initialize up to this point.
*/
for (i = 0; i < log_2-1; i++) {
w[i][0] = ct[2*i][0];
w[i][1] = ct[2*i][1];
}
Expand All @@ -1073,11 +1081,11 @@ ffts_generate_table_1d_real_32f(struct _ffts_plan_t *const p,
float t0, t1, t2;

/* calculate trailing zeros in index */
log_2 = ffts_ctzl(i);
int i_log_2 = ffts_ctzl(i);

t0 = (float) (0.5 * (1.0 - w[log_2][1]));
t1 = (float) (0.5 * w[log_2][0]);
t2 = (float) (0.5 * (1.0 + w[log_2][1]));
t0 = (float) (0.5 * (1.0 - w[i_log_2][1]));
t1 = (float) (0.5 * w[i_log_2][0]);
t2 = (float) (0.5 * (1.0 + w[i_log_2][1]));

A[ 2 * i + 0] = t0;
A[N - 2 * i + 0] = t0;
Expand All @@ -1090,20 +1098,20 @@ ffts_generate_table_1d_real_32f(struct _ffts_plan_t *const p,
B[N - 2 * i + 1] = -t1;

/* skip and find next trailing zero */
offset = (log_2 + 2 + ffts_ctzl(~i >> (log_2 + 2)));
w[log_2][0] = hs[2 * log_2].d * (w[log_2 + 1][0] + w[offset][0]);
w[log_2][1] = hs[2 * log_2].d * (w[log_2 + 1][1] + w[offset][1]);
offset = (i_log_2 + 2 + ffts_ctzl(~i >> (i_log_2 + 2)));
w[i_log_2][0] = hs[2 * i_log_2].d * (w[i_log_2 + 1][0] + w[offset][0]);
w[i_log_2][1] = hs[2 * i_log_2].d * (w[i_log_2 + 1][1] + w[offset][1]);
}
} else {
for (i = 1; i < N/4; i++) {
float t0, t1, t2;

/* calculate trailing zeros in index */
log_2 = ffts_ctzl(i);
int i_log_2 = ffts_ctzl(i);

t0 = (float) (1.0 - w[log_2][1]);
t1 = (float) w[log_2][0];
t2 = (float) (1.0 + w[log_2][1]);
t0 = (float) (1.0 - w[i_log_2][1]);
t1 = (float) w[i_log_2][0];
t2 = (float) (1.0 + w[i_log_2][1]);

A[ 2 * i + 0] = t0;
A[N - 2 * i + 0] = t0;
Expand All @@ -1116,9 +1124,9 @@ ffts_generate_table_1d_real_32f(struct _ffts_plan_t *const p,
B[N - 2 * i + 1] = -t1;

/* skip and find next trailing zero */
offset = (log_2 + 2 + ffts_ctzl(~i >> (log_2 + 2)));
w[log_2][0] = hs[2 * log_2].d * (w[log_2 + 1][0] + w[offset][0]);
w[log_2][1] = hs[2 * log_2].d * (w[log_2 + 1][1] + w[offset][1]);
offset = (i_log_2 + 2 + ffts_ctzl(~i >> (i_log_2 + 2)));
w[i_log_2][0] = hs[2 * i_log_2].d * (w[i_log_2 + 1][0] + w[offset][0]);
w[i_log_2][1] = hs[2 * i_log_2].d * (w[i_log_2 + 1][1] + w[offset][1]);
}
}

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