[PATCH 4.14 181/222] kgdboc: Passing ekgdboc to command line causes panic

Greg Kroah-Hartman
2018-11-11T22:49:46Z

From: He Zhe <zhe.he@windriver.com>

commit 1bd54d851f50dea6af30c3e6ff4f3e9aab5558f9 upstream.

kgdboc_option_setup does not check input argument before passing it
to strlen. The argument would be a NULL pointer if "ekgdboc", without
its value, is set in command line and thus cause the following panic.

PANIC: early exception 0xe3 IP 10:ffffffff8fbbb620 error 0 cr2 0x0
[ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.18-rc8+ #1
[ 0.000000] RIP: 0010:strlen+0x0/0x20
...
[ 0.000000] Call Trace
[ 0.000000] ? kgdboc_option_setup+0x9/0xa0
[ 0.000000] ? kgdboc_early_init+0x6/0x1b
[ 0.000000] ? do_early_param+0x4d/0x82
[ 0.000000] ? parse_args+0x212/0x330
[ 0.000000] ? rdinit_setup+0x26/0x26
[ 0.000000] ? parse_early_options+0x20/0x23
[ 0.000000] ? rdinit_setup+0x26/0x26
[ 0.000000] ? parse_early_param+0x2d/0x39
[ 0.000000] ? setup_arch+0x2f7/0xbf4
[ 0.000000] ? start_kernel+0x5e/0x4c2
[ 0.000000] ? load_ucode_bsp+0x113/0x12f
[ 0.000000] ? secondary_startup_64+0xa5/0xb0

This patch adds a check to prevent the panic.

Cc: stable@vger.kernel.org
Cc: jason.wessel@windriver.com
Cc: gregkh@linuxfoundation.org
Cc: jslaby@suse.com
Signed-off-by: He Zhe <zhe.he@windriver.com>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/tty/serial/kgdboc.c | 5 +++++
1 file changed, 5 insertions(+)

--- a/drivers/tty/serial/kgdboc.c
+++ b/drivers/tty/serial/kgdboc.c
@@ -133,6 +133,11 @@ static void kgdboc_unregister_kbd(void)

static int kgdboc_option_setup(char *opt)
{
+ if (!opt) {
+ pr_err("kgdboc: config string not provided\n");
+ return -EINVAL;
+ }
+
if (strlen(opt) >= MAX_CONFIG_LEN) {
printk(KERN_ERR "kgdboc: config string too long\n");
return -ENOSPC;