The existing code attempted to handle numbers by doing a strto[u]l(), ignoring the field width, and then bitshifting the field out of the converted value. If the string contains a run of valid digits longer than will fit in a long or long long, this would overflow and no amount of bitshifting can recover the correct value.
This patch fixes vsscanf to obey number field widths. A new _parse_integer_limit() is added that takes a limit for the number of characters to parse. A length of INT_MAX is effectively unlimited, as we are not likely to need parsing of digit strings >INT_MAX length. The number field conversion in vsscanf is changed to use this new _parse_integer_limit() function so that field widths are obeyed when parsing the number. Note also that the conversion is always done as a long long - as there's currently no overflow checking there is no point implementing separate long and long long conversions. Signed-off-by: Richard Fitzgerald <[email protected]> --- lib/kstrtox.c | 14 ++++++++--- lib/kstrtox.h | 2 ++ lib/vsprintf.c | 65 +++++++++++++++++++++++++++----------------------- 3 files changed, 48 insertions(+), 33 deletions(-) diff --git a/lib/kstrtox.c b/lib/kstrtox.c index a14ccf905055..9867501a4ab0 100644 --- a/lib/kstrtox.c +++ b/lib/kstrtox.c @@ -39,20 +39,23 @@ const char *_parse_integer_fixup_radix(const char *s, unsigned int *base) /* * Convert non-negative integer string representation in explicitly given radix - * to an integer. + * to an integer. The maximum number of characters to convert can be given. + * A character limit of INT_MAX is effectively unlimited since a string that + * long is unreasonable. * Return number of characters consumed maybe or-ed with overflow bit. * If overflow occurs, result integer (incorrect) is still returned. * * Don't you dare use this function. */ -unsigned int _parse_integer(const char *s, unsigned int base, unsigned long long *p) +unsigned int _parse_integer_limit(const char *s, unsigned int base, unsigned long long *p, + int max_chars) { unsigned long long res; unsigned int rv; res = 0; rv = 0; - while (1) { + for (; max_chars > 0; max_chars--) { unsigned int c = *s; unsigned int lc = c | 0x20; /* don't tolower() this line */ unsigned int val; @@ -82,6 +85,11 @@ unsigned int _parse_integer(const char *s, unsigned int base, unsigned long long return rv; } +unsigned int _parse_integer(const char *s, unsigned int base, unsigned long long *p) +{ + return _parse_integer_limit(s, base, p, INT_MAX); +} + static int _kstrtoull(const char *s, unsigned int base, unsigned long long *res) { unsigned long long _res; diff --git a/lib/kstrtox.h b/lib/kstrtox.h index 3b4637bcd254..4e5dfa3437dc 100644 --- a/lib/kstrtox.h +++ b/lib/kstrtox.h @@ -4,6 +4,8 @@ #define KSTRTOX_OVERFLOW (1U << 31) const char *_parse_integer_fixup_radix(const char *s, unsigned int *base); +unsigned int _parse_integer_limit(const char *s, unsigned int base, + unsigned long long *res, int max_chars); unsigned int _parse_integer(const char *s, unsigned int base, unsigned long long *res); #endif diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 14c9a6af1b23..8ec47b5da2cb 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -53,6 +53,25 @@ #include <linux/string_helpers.h> #include "kstrtox.h" +static unsigned long long simple_strntoull(const char *startp, int max_chars, + char **endp, unsigned int base) +{ + const char *cp; + unsigned long long result; + unsigned int rv; + + cp = _parse_integer_fixup_radix(startp, &base); + max_chars -= (cp - startp); + rv = _parse_integer_limit(cp, base, &result, max_chars); + /* FIXME */ + cp += (rv & ~KSTRTOX_OVERFLOW); + + if (endp) + *endp = (char *)cp; + + return result; +} + /** * simple_strtoull - convert a string to an unsigned long long * @cp: The start of the string @@ -63,18 +82,7 @@ */ unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int base) { - unsigned long long result; - unsigned int rv; - - cp = _parse_integer_fixup_radix(cp, &base); - rv = _parse_integer(cp, base, &result); - /* FIXME */ - cp += (rv & ~KSTRTOX_OVERFLOW); - - if (endp) - *endp = (char *)cp; - - return result; + return simple_strntoull(cp, INT_MAX, endp, base); } EXPORT_SYMBOL(simple_strtoull); @@ -126,6 +134,15 @@ long long simple_strtoll(const char *cp, char **endp, unsigned int base) } EXPORT_SYMBOL(simple_strtoll); +static long long simple_strntoll(const char *cp, int max_chars, char **endp, + unsigned int base) +{ + if (*cp == '-') + return -simple_strntoull(cp + 1, max_chars - 1, endp, base); + + return simple_strntoull(cp, max_chars, endp, base); +} + static noinline_for_stack int skip_atoi(const char **s) { @@ -3444,25 +3461,13 @@ int vsscanf(const char *buf, const char *fmt, va_list args) break; if (is_sign) - val.s = qualifier != 'L' ? - simple_strtol(str, &next, base) : - simple_strtoll(str, &next, base); + val.s = simple_strntoll(str, + field_width > 0 ? field_width : INT_MAX, + &next, base); else - val.u = qualifier != 'L' ? - simple_strtoul(str, &next, base) : - simple_strtoull(str, &next, base); - - if (field_width > 0 && next - str > field_width) { - if (base == 0) - _parse_integer_fixup_radix(str, &base); - while (next - str > field_width) { - if (is_sign) - val.s = div_s64(val.s, base); - else - val.u = div_u64(val.u, base); - --next; - } - } + val.u = simple_strntoull(str, + field_width > 0 ? field_width : INT_MAX, + &next, base); switch (qualifier) { case 'H': /* that's 'hh' in format */ -- 2.20.1
