misc: kgdbts: fix out-of-bounds access in function param_set_kgdbts_var

There is an out-of-bounds access to "config[len - 1]" array when the
variable "len" is zero.

See commit dada6a43b040 ("kgdboc: fix KASAN global-out-of-bounds bug
in param_set_kgdboc_var()") for details.

Signed-off-by: Young Xiao <YangX92@hotmail.com>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/misc/kgdbts.c b/drivers/misc/kgdbts.c
index de20bdaa148d..8b01257783dd 100644
--- a/drivers/misc/kgdbts.c
+++ b/drivers/misc/kgdbts.c
@@ -1135,7 +1135,7 @@ static void kgdbts_put_char(u8 chr)
 static int param_set_kgdbts_var(const char *kmessage,
                                 const struct kernel_param *kp)
 {
-        int len = strlen(kmessage);
+        size_t len = strlen(kmessage);
 
         if (len >= MAX_CONFIG_LEN) {
                 printk(KERN_ERR "kgdbts: config string too long\n");
@@ -1155,7 +1155,7 @@ static int param_set_kgdbts_var(const char *kmessage,
 
         strcpy(config, kmessage);
         /* Chop out \n char as a result of echo */
-        if (config[len - 1] == '\n')
+        if (len && config[len - 1] == '\n')
                 config[len - 1] = '\0';
 
         /* Go and configure with the new params. */