[PATCH] rev-parse --parseopt: detect missing opt-spec

["Øystein Walle" <oystwa@gmail.com>]

After 2d893dff4c (rev-parse --parseopt: allow [*=?!] in argument hints,
2015-07-14) updated the parser, a line in parseopts's input can start
with one of the flag characters and be erroneously parsed as a opt-spec
where the short name of the option is the flag character itself and the
long name is after the end of the string. This makes Git want to
allocate SIZE_MAX bytes of memory at this line:

    o->long_name = xmemdupz(sb.buf + 2, s - sb.buf - 2);

Since s and sb.buf are equal the second argument is -2 (except unsigned)
and xmemdupz allocates len + 1 bytes, ie. -1 meaning SIZE_MAX.

Avoid this by checking whether a flag character was found in the zeroth
position.

Reported-by: Ingy dot Net <ingy@ingy.net>
Reviewed-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Øystein Walle <oystwa@gmail.com>
---

Hi guys, thanks for the review. I incorporated a reference to the old
commit into the message (and took the liberty of adding --parseopt to
the subject like it had). I tried to verify that it was in fact this
commit, since the code prior to this one had the exact same xmemdupz()
call. I wasn't able to build that commit, and reverting it also wasn't
straightforward. But I'm fairly confident it's the case since the old
call had an if similar to the one added here.

I completely agree with the changes to the test; it makes little sense
to mix stdout and stderr here.

Jeff, I agree that perhaps a larger rewrite would be better. I
personally can get easily confused by "sporadic" ifs like this one in
the middle of a piece of code. At least in this case the message within
die() neatly explains what's going on.

Øsse

 builtin/rev-parse.c           | 3 +++
 t/t1502-rev-parse-parseopt.sh | 7 +++++++
 2 files changed, 10 insertions(+)

diff --git a/builtin/rev-parse.c b/builtin/rev-parse.c
index b259d8990a..85c271acd7 100644
--- a/builtin/rev-parse.c
+++ b/builtin/rev-parse.c
@@ -479,6 +479,9 @@ static int cmd_parseopt(int argc, const char **argv, const char *prefix)
 		if (!s)
 			s = help;
 
+		if (s == sb.buf)
+			die(_("missing opt-spec before option flags"));
+
 		if (s - sb.buf == 1) /* short option only */
 			o->short_name = *sb.buf;
 		else if (sb.buf[1] != ',') /* long option only */
diff --git a/t/t1502-rev-parse-parseopt.sh b/t/t1502-rev-parse-parseopt.sh
index 284fe18e72..de1d48f3ba 100755
--- a/t/t1502-rev-parse-parseopt.sh
+++ b/t/t1502-rev-parse-parseopt.sh
@@ -306,6 +306,13 @@ test_expect_success 'test --parseopt help output: "wrapped" options normal "or:"
 	test_cmp expect actual
 '
 
+test_expect_success 'test --parseopt invalid opt-spec' '
+	test_write_lines x -- "=, x" >spec &&
+	echo "fatal: missing opt-spec before option flags" >expect &&
+	test_must_fail git rev-parse --parseopt -- >out <spec 2>err &&
+	test_cmp expect err
+'
+
 test_expect_success 'test --parseopt help output: multi-line blurb after empty line' '
 	sed -e "s/^|//" >spec <<-\EOF &&
 	|cmd [--some-option]
-- 
2.34.1