Subject: Re: [BUG] rev-list doesn't validate arguments to -n option

From: Junio C Hamano <[email-masked]>
Date: Sat, 09 Dec 2023 05:36:30 +0900

Britton Kerin <[email-masked]> writes:

> It tolerates non-numeric arguments and garbage after a number:
>
> For example:
>
> $ # -n 1 means same as -n 0:
> $ git rev-list -n q newest_commit
> $ git rev-list -n 0 newest_commit
> $ # Garbage after number is tolerated:
> $ git rev-list -n 1q newest_commit
> 3be33f83695088d968cf084a1a08bdcde25a8d7a
> $ git rev-list -n 2q newest_commit
> 3be33f83695088d968cf084a1a08bdcde25a8d7a
> 286e62e1b68e39334978e6222cbff187ecc17bcf

Indeed, unlike the option parsing for most commands, "rev-list" and
"log" family of commands in the oldest part of the system still use
hand-crafted option parsing and most notably use atoi() instead of a
more robust strtol() family of functions.  The same issue is present
for parsing things like "--max-count=1q" and "--skip=1q".

Perhaps a change along this line, plus a few new tests, would
suffice.  There are others (like "--max-age" we see in the post
context of the patch) that use atoi() but they probably should not
share the same machinery (most importantly, the type of the value)
as "--max-count", so I didn't touch it in the below.

 revision.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git c/revision.c w/revision.c
index 00d5c29bfc..99e838bbd1 100644
--- c/revision.c
+++ w/revision.c
@@ -2223,6 +2223,15 @@ static void add_message_grep(struct rev_info *revs, const char *pattern)
 	add_grep(revs, pattern, GREP_PATTERN_BODY);
 }
 
+static int parse_count(const char *arg)
+{
+	int count;
+
+	if (strtol_i(arg, 10, &count) < 0 || count < 0)
+		die("'%s': not a non-negative integer", arg);
+	return count;
+}
+
 static int handle_revision_opt(struct rev_info *revs, int argc, const char **argv,
 			       int *unkc, const char **unkv,
 			       const struct setup_revision_opt* opt)
@@ -2249,26 +2258,24 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 	}
 
 	if ((argcount = parse_long_opt("max-count", argv, &optarg))) {
-		revs->max_count = atoi(optarg);
+		revs->max_count = parse_count(optarg);
 		revs->no_walk = 0;
 		return argcount;
 	} else if ((argcount = parse_long_opt("skip", argv, &optarg))) {
-		revs->skip_count = atoi(optarg);
+		revs->skip_count = parse_count(optarg);
 		return argcount;
 	} else if ((*arg == '-') && isdigit(arg[1])) {
 		/* accept -<digit>, like traditional "head" */
-		if (strtol_i(arg + 1, 10, &revs->max_count) < 0 ||
-		    revs->max_count < 0)
-			die("'%s': not a non-negative integer", arg + 1);
+		revs->max_count = parse_count(arg + 1);
 		revs->no_walk = 0;
 	} else if (!strcmp(arg, "-n")) {
 		if (argc <= 1)
 			return error("-n requires an argument");
-		revs->max_count = atoi(argv[1]);
+		revs->max_count = parse_count(argv[1]);
 		revs->no_walk = 0;
 		return 2;
 	} else if (skip_prefix(arg, "-n", &optarg)) {
-		revs->max_count = atoi(optarg);
+		revs->max_count = parse_count(optarg);
 		revs->no_walk = 0;
 	} else if ((argcount = parse_long_opt("max-age", argv, &optarg))) {
 		revs->max_age = atoi(optarg);