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Subject[PATCH] kgdboc: Passing ekgdboc to command line causes panic
Date
From: He Zhe <zhe.he@windriver.com>

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 and changes some printk
to right fashion.

Signed-off-by: He Zhe <zhe.he@windriver.com>
---
drivers/tty/serial/kgdboc.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c
index b4ba2b1..0003d6c 100644
--- a/drivers/tty/serial/kgdboc.c
+++ b/drivers/tty/serial/kgdboc.c
@@ -130,8 +130,13 @@ static void kgdboc_unregister_kbd(void)

static int kgdboc_option_setup(char *opt)
{
+ if (!opt) {
+ pr_err("kgdboc: null option\n");
+ return -EINVAL;
+ }
+
if (strlen(opt) >= MAX_CONFIG_LEN) {
- printk(KERN_ERR "kgdboc: config string too long\n");
+ pr_err("kgdboc: config string too long\n");
return -ENOSPC;
}
strcpy(config, opt);
@@ -248,7 +253,7 @@ static int param_set_kgdboc_var(const char *kmessage,
int len = strlen(kmessage);

if (len >= MAX_CONFIG_LEN) {
- printk(KERN_ERR "kgdboc: config string too long\n");
+ pr_err("kgdboc: config string too long\n");
return -ENOSPC;
}

@@ -259,8 +264,7 @@ static int param_set_kgdboc_var(const char *kmessage,
}

if (kgdb_connected) {
- printk(KERN_ERR
- "kgdboc: Cannot reconfigure while KGDB is connected.\n");
+ pr_err("kgdboc: Cannot reconfigure while KGDB is connected.\n");

return -EBUSY;
}
--
2.7.4
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