linux-kernel - [PATCH 1/6] kconfig: require a space after '#' for valid input

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Message-Id: <20231118075912.1303509-1-masahiroy@kernel.org>
Date:   Sat, 18 Nov 2023 16:59:07 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     linux-kbuild@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Masahiro Yamada <masahiroy@...nel.org>
Subject: [PATCH 1/6] kconfig: require a space after '#' for valid input

Currently, when an input line starts with '#', (line + 2) is passed to
memcmp() without checking line[1].

It means that line[1] can be any arbitrary character. For example,
"#KCONFIG_FOO is not set" is accepted as valid input, functioning the
same as "# CONFIG_FOO is not set".

More importantly, this can potentially lead to a buffer overrun if
line[1] == '\0'. It occurs if the input only contains '#', as
(line + 2) points to an uninitialized buffer.

Check line[1], and skip the line if it is not a space.

Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
---

 scripts/kconfig/confdata.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/scripts/kconfig/confdata.c b/scripts/kconfig/confdata.c
index 2ba4dfdd1aee..556b7f087dbb 100644
--- a/scripts/kconfig/confdata.c
+++ b/scripts/kconfig/confdata.c
@@ -426,6 +426,8 @@ int conf_read_simple(const char *name, int def)
 		conf_lineno++;
 		sym = NULL;
 		if (line[0] == '#') {
+			if (line[1] != ' ')
+				continue;
 			if (memcmp(line + 2, CONFIG_, strlen(CONFIG_)))
 				continue;
 			p = strchr(line + 2 + strlen(CONFIG_), ' ');
-- 
2.40.1