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AP_GPS: prevent bad NMEA strings from causing overruns in parser

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fixes issue #961

thanks to crashpilot100 for spotting this!
This commit is contained in:
Andrew Tridgell 2014-11-16 14:08:20 +11:00
parent c52578426e
commit b81b9e1bb8
1 changed files with 6 additions and 4 deletions
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10
libraries/AP_GPS/AP_GPS_NMEA.cpp
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@ -105,6 +105,8 @@ AP_GPS_NMEA::AP_GPS_NMEA(AP_GPS &_gps, AP_GPS::GPS_State &_state, AP_HAL::UARTDr
_gps_data_good(false)
{
gps.send_blob_start(state.instance, _initialisation_blob, sizeof(_initialisation_blob));
// this guarantees that _term is always nul terminated
memset(_term, 0, sizeof(_term));
}
bool AP_GPS_NMEA::read(void)
@ -198,19 +200,19 @@ uint32_t AP_GPS_NMEA::_parse_degrees()
int32_t ret = 0;
// scan for decimal point or end of field
for (p = _term; isdigit(*p); p++)
for (p = _term; *p && isdigit(*p); p++)
;
q = _term;
// convert degrees
while ((p - q) > 2) {
while ((p - q) > 2 && *q) {
if (deg)
deg *= 10;
deg += DIGIT_TO_VAL(*q++);
}
// convert minutes
while (p > q) {
while (p > q && *q) {
if (min)
min *= 10;
min += DIGIT_TO_VAL(*q++);
@ -220,7 +222,7 @@ uint32_t AP_GPS_NMEA::_parse_degrees()
if (*p == '.') {
q = p + 1;
float frac_scale = 0.1f;
while (isdigit(*q)) {
while (*q && isdigit(*q)) {
frac_min += (*q++ - '0') * frac_scale;
frac_scale *= 0.1f;
}