[PATCH AUTOSEL 4.19 08/36] Drivers: misc: fix out-of-bounds access in function param_set_kgdbts_var

[Sasha Levin]

From: Young Xiao <yang...@hotmail.com>

[ Upstream commit b281218ad4311a0342a40cb02fb17a363df08b48 ]

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 <yang...@hotmail.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
 drivers/misc/kgdbts.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/kgdbts.c b/drivers/misc/kgdbts.c
index 6193270e7b3d..eb4d90b7d99e 100644
--- a/drivers/misc/kgdbts.c
+++ b/drivers/misc/kgdbts.c
@@ -1139,7 +1139,7 @@ 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");
@@ -1159,7 +1159,7 @@ 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. */
-- 
2.20.1