git_parse_unsigned: reject negative values

git_parse_unsigned() relies on strtoumax() which unfortunately parses
negative values as large positive integers. Fix this by rejecting any
string that contains '-' as we do in strtoul_ui(). I've chosen to treat
negative numbers as invalid input and set errno to EINVAL rather than
ERANGE one the basis that they are never acceptable if we're looking for
a unsigned integer. This is also consistent with the existing behavior
of rejecting "1–2" with EINVAL.

As we do not have unit tests for this function it is tested indirectly
by checking that negative values of reject for core.bigFileThreshold are
rejected. As this function is also used by OPT_MAGNITUDE() a test is
added to check that rejects negative values too.

Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Taylor Blau <me@ttaylorr.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/config.c b/config.c
index cbb5a3b..d5069d4 100644
--- a/config.c
+++ b/config.c
@@ -1193,6 +1193,11 @@ static int git_parse_unsigned(const char *value, uintmax_t *ret, uintmax_t max)
 		uintmax_t val;
 		uintmax_t factor;
 
+		/* negative values would be accepted by strtoumax */
+		if (strchr(value, '-')) {
+			errno = EINVAL;
+			return 0;
+		}
 		errno = 0;
 		val = strtoumax(value, &end, 0);
 		if (errno == ERANGE)