[PATCH 2/3] batctl: version: avoid use of uninitialized read buffer

[Sven Eckelmann <sven@narfation.org>]

version() strips the trailing newline from line_ptr before checking whether
read_file() actually succeeded. If the read_file() returned an error, it
could be that line_ptr was allocated buyt not yet initialized. It could
therefore not contain any \0 delimiter - making the strlen read outside the
buffer. The write of the \0 could therefore also be outside the buffer.

Only attempt to access the buffer when a success was indicated.

Fixes: dbc4a8c8e585 ("batctl: version also prints the kernel module version if available")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
 main.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/main.c b/main.c
index 79ed4ef..e625291 100644
--- a/main.c
+++ b/main.c
@@ -132,13 +132,14 @@ static void version(void)
 	printf("batctl %s [batman-adv: ", SOURCE_VERSION);
 
 	ret = read_file(module_ver_path, USE_READ_BUFF | SILENCE_ERRORS);
-	if ((line_ptr) && (line_ptr[strlen(line_ptr) - 1] == '\n'))
-		line_ptr[strlen(line_ptr) - 1] = '\0';
+	if (ret == EXIT_SUCCESS) {
+		if (line_ptr[strlen(line_ptr) - 1] == '\n')
+			line_ptr[strlen(line_ptr) - 1] = '\0';
 
-	if (ret == EXIT_SUCCESS)
 		printf("%s]\n", line_ptr);
-	else
+	} else {
 		printf("module version unknown]\n");
+	}
 
 	free(line_ptr);
 	exit(EXIT_SUCCESS);

-- 
2.47.3