kgdboc,tty: Fix tty polling search to use name correctly

The tty_find_polling_driver() routine did not correctly check the base
part of the tty name.  This can lead to kgdboc selecting an incorrect
driver, as well as accepting a completely invalid tty such as "echo
ffff0 > /sys/module/kgdboc/parameters/kgdboc".

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>

1 files changed, 12 insertions, 2 deletions

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index daeb8f766971..e4dce8709541 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -695,13 +695,23 @@ struct tty_driver *tty_find_polling_driver(char *name, int *line)
 {
         struct tty_driver *p, *res = NULL;
         int tty_line = 0;
+        int len;
         char *str;
 
+        for (str = name; *str; str++)
+                if ((*str >= '0' && *str <= '9') || *str == ',')
+                        break;
+        if (!*str)
+                return NULL;
+
+        len = str - name;
+        tty_line = simple_strtoul(str, &str, 10);
+
         mutex_lock(&tty_mutex);
         /* Search through the tty devices to look for a match */
         list_for_each_entry(p, &tty_drivers, tty_drivers) {
-                str = name + strlen(p->name);
-                tty_line = simple_strtoul(str, &str, 10);
+                if (strncmp(name, p->name, len) != 0)
+                        continue;
                 if (*str == ',')
                         str++;
                 if (*str == '\0')