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Patch from Lorenzo to avoid memory corruption in bignum sqrt.

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This commit is contained in:
Alex Shinn 2014-01-27 08:58:56 +09:00
parent 4a4f626956
commit b890b2f4a5
1 changed files with 6 additions and 1 deletions
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7
bignum.c
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@ -87,11 +87,14 @@ sexp sexp_copy_bignum (sexp ctx, sexp dst, sexp a, sexp_uint_t len0) {
dst = sexp_alloc_tagged(ctx, size, SEXP_BIGNUM); dst = sexp_alloc_tagged(ctx, size, SEXP_BIGNUM);
sexp_bignum_length(dst) = len; sexp_bignum_length(dst) = len;
} }
if (sexp_bignum_length(a) < len)
len = sexp_bignum_length(a);
sexp_bignum_sign(dst) = sexp_bignum_sign(a); sexp_bignum_sign(dst) = sexp_bignum_sign(a);
memset(sexp_bignum_data(dst), 0, memset(sexp_bignum_data(dst), 0,
sexp_bignum_length(dst)*sizeof(sexp_uint_t)); sexp_bignum_length(dst)*sizeof(sexp_uint_t));
memmove(sexp_bignum_data(dst), sexp_bignum_data(a), memmove(sexp_bignum_data(dst), sexp_bignum_data(a),
sexp_bignum_length(a)*sizeof(sexp_uint_t)); len*sizeof(sexp_uint_t));
return dst; return dst;
} }
@ -594,6 +597,8 @@ sexp sexp_bignum_sqrt (sexp ctx, sexp a) { /* Babylonian method */
res = sexp_sqrt(ctx, NULL, 1, res); res = sexp_sqrt(ctx, NULL, 1, res);
if (sexp_flonump(res) && if (sexp_flonump(res) &&
sexp_flonum_value(res) > SEXP_MAX_ACCURATE_FLONUM_SQRT) { sexp_flonum_value(res) > SEXP_MAX_ACCURATE_FLONUM_SQRT) {
if (!isfinite(sexp_flonum_value(res)))
res = sexp_make_flonum(ctx, 1e+154);
res = sexp_double_to_bignum(ctx, sexp_flonum_value(res)); res = sexp_double_to_bignum(ctx, sexp_flonum_value(res));
loop: /* until 0 <= a - res*res < 2*res + 1 */ loop: /* until 0 <= a - res*res < 2*res + 1 */
rem = sexp_mul(ctx, res, res); rem = sexp_mul(ctx, res, res);