On 29/03/2021 14:36, Andy Shevchenko wrote:
On Mon, Mar 29, 2021 at 01:08:22PM +0100, Richard Fitzgerald wrote:The existing code attempted to handle numbers by doing a strto[u]l(), ignoring the field width, and then repeatedly dividing to extract the field out of the full 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 dividing can recover the correct value. This patch fixes vsscanf() to obey number field widths when parsing the number. A new _parse_integer_limit() is added that takes a limit for the number of characters to parse. The number field conversion in vsscanf is changed to use this new function. If a number starts with a radix prefix, the field width must be long enough for at last one digit after the prefix. If not, it will be handled like this: sscanf("0x4", "%1i", &i): i=0, scanning continues with the 'x' sscanf("0x4", "%2i", &i): i=0, scanning continues with the '4' This is consistent with the observed behaviour of userland sscanf. Note that this patch does NOT fix the problem of a single field value overflowing the target type. So for example: sscanf("123456789abcdef", "%x", &i); Will not produce the correct result because the value obviously overflows INT_MAX. But sscanf will report a successful conversion. Note that where a very large number is used to mean "unlimited", the value INT_MAX is used for consistency with the behaviour of vsnprintf()....unsigned long simple_strtoul(const char *cp, char **endp, unsigned int base) { - return simple_strtoull(cp, endp, base); + return simple_strntoull(cp, INT_MAX, endp, base);Why do you need this change?
I agree it's not necessary. I changed it between V1 and V2 but I can't remember what the reason was.
