[PATCH v2 1/3] git_parse_unsigned: reject negative values

["Phillip Wood via GitGitGadget" <gitgitgadget@gmail.com>]

From: Phillip Wood <phillip.wood@dunelm.org.uk>

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>
---
 config.c                 | 5 +++++
 t/t0040-parse-options.sh | 5 +++++
 t/t1050-large.sh         | 6 ++++++
 3 files changed, 16 insertions(+)

diff --git a/config.c b/config.c
index cbb5a3bab74..d5069d4f01d 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)
diff --git a/t/t0040-parse-options.sh b/t/t0040-parse-options.sh
index 5cc62306e39..64d2327b744 100755
--- a/t/t0040-parse-options.sh
+++ b/t/t0040-parse-options.sh
@@ -709,4 +709,9 @@ test_expect_success 'subcommands are incompatible with KEEP_DASHDASH unless in c
 	grep ^BUG err
 '
 
+test_expect_success 'negative magnitude' '
+	test_must_fail test-tool parse-options --magnitude -1 >out 2>err &&
+	grep "non-negative integer" err &&
+	test_must_be_empty out
+'
 test_done
diff --git a/t/t1050-large.sh b/t/t1050-large.sh
index 4f3aa17c994..c71932b0242 100755
--- a/t/t1050-large.sh
+++ b/t/t1050-large.sh
@@ -5,6 +5,12 @@ test_description='adding and checking out large blobs'
 
 . ./test-lib.sh
 
+test_expect_success 'core.bigFileThreshold must be non-negative' '
+	test_must_fail git -c core.bigFileThreshold=-1 rev-parse >out 2>err &&
+	grep "bad numeric config value" err &&
+	test_must_be_empty out
+'
+
 test_expect_success setup '
 	# clone does not allow us to pass core.bigfilethreshold to
 	# new repos, so set core.bigfilethreshold globally
-- 
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