From ee96a273969b0bccd308b81bcdf37a6fdefa06f6 Mon Sep 17 00:00:00 2001 From: Silviu Baranga Date: Mon, 5 Jun 2017 09:54:42 +0100 Subject: [PATCH] Don't overread or write memory returned by _DTOA_R Don't over-read memory returned by _DTOA_R, and never write to it since the result might be a string literal. For example, when doing: swprintf(tt, 20, L"%.*f", 6, 0.0); we will get back "0". Instead, write the result returned by _DTOA_R to the output buffer. After this, write the 0 chars directly to the the output buffer (if there are any). This also has the (marginal) advantage that we read/write less memory overall. --- newlib/libc/stdio/vfwprintf.c | 25 +++++++++++++------------ 1 file changed, 13 insertions(+), 12 deletions(-) diff --git a/newlib/libc/stdio/vfwprintf.c b/newlib/libc/stdio/vfwprintf.c index f0179a0..eb5a2dc 100644 --- a/newlib/libc/stdio/vfwprintf.c +++ b/newlib/libc/stdio/vfwprintf.c @@ -1627,12 +1627,18 @@ wcvt(struct _reent *data, _PRINTF_FLOAT_TYPE value, int ndigits, int flags, { char *digits, *bp, *rve; -#ifndef _MB_CAPABLE int i; -#endif digits = _DTOA_R (data, value, mode, ndigits, decpt, &dsgn, &rve); +#ifdef _MB_CAPABLE + _mbsnrtowcs_r (data, buf, (const char **) &digits, rve - digits, + len, NULL); +#else + for (i = 0; i < rve - digits && i < len; ++i) + buf[i] = (wchar_t) digits[i]; +#endif + if ((ch != L'g' && ch != L'G') || flags & ALT) { /* Print trailing zeros */ bp = digits + ndigits; if (ch == L'f' || ch == L'F') { @@ -1642,18 +1648,13 @@ wcvt(struct _reent *data, _PRINTF_FLOAT_TYPE value, int ndigits, int flags, } if (value == 0) /* kludge for __dtoa irregularity */ rve = bp; - while (rve < bp) - *rve++ = '0'; - } + for (i = rve - digits; i < bp - digits && i < len; ++i) + buf[i] = L'0'; + + rve = rve > bp ? rve : bp; + } *length = rve - digits; /* full length of the string */ -#ifdef _MB_CAPABLE - _mbsnrtowcs_r (data, buf, (const char **) &digits, *length, - len, NULL); -#else - for (i = 0; i < *length && i < len; ++i) - buf[i] = (wchar_t) digits[i]; -#endif return buf; } } -- 1.9.1