linux-kernel - [PATCH 5.4 164/183] kconfig: fix infinite loop when expanding a macro at the end of file

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Message-ID: <20240324234638.1355609-165-sashal@kernel.org>
Date: Sun, 24 Mar 2024 19:46:17 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Masahiro Yamada <masahiroy@...nel.org>,
	Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 164/183] kconfig: fix infinite loop when expanding a macro at the end of file

From: Masahiro Yamada <masahiroy@...nel.org>

[ Upstream commit af8bbce92044dc58e4cc039ab94ee5d470a621f5 ]

A macro placed at the end of a file with no newline causes an infinite
loop.

[Test Kconfig]
  $(info,hello)
  \ No newline at end of file

I realized that flex-provided input() returns 0 instead of EOF when it
reaches the end of a file.

Fixes: 104daea149c4 ("kconfig: reference environment variables directly and remove 'option env='")
Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 scripts/kconfig/lexer.l | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/scripts/kconfig/lexer.l b/scripts/kconfig/lexer.l
index 6354c905b006f..3bf90d01c39f9 100644
--- a/scripts/kconfig/lexer.l
+++ b/scripts/kconfig/lexer.l
@@ -305,8 +305,11 @@ static char *expand_token(const char *in, size_t n)
 	new_string();
 	append_string(in, n);
 
-	/* get the whole line because we do not know the end of token. */
-	while ((c = input()) != EOF) {
+	/*
+	 * get the whole line because we do not know the end of token.
+	 * input() returns 0 (not EOF!) when it reachs the end of file.
+	 */
+	while ((c = input()) != 0) {
 		if (c == '\n') {
 			unput(c);
 			break;
-- 
2.43.0