chardev: add a check for given minor range

register_chrdev_region() carefully checks minor range
before calling __register_chrdev_region() but there is
another path from alloc_chrdev_region() which does not
check the range properly. So add a check for given minor
range in __register_chrdev_region().

Signed-off-by: Chengguang Xu <cgxu519@gmx.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/fs/char_dev.c b/fs/char_dev.c
index 8a63cfa29005..6803e98414f1 100644
--- a/fs/char_dev.c
+++ b/fs/char_dev.c
@@ -104,6 +104,12 @@ __register_chrdev_region(unsigned int major, unsigned int baseminor,
         int ret = 0;
         int i;
 
+        if (minorct > MINORMASK + 1 - baseminor) {
+                pr_err("CHRDEV \"%s\" minor range requested (%u-%u) is out of range of maximum range (%u-%u) for a single major\n",
+                        name, baseminor, baseminor + minorct - 1, 0, MINORMASK);
+                return ERR_PTR(-EINVAL);
+        }
+
         cd = kzalloc(sizeof(struct char_device_struct), GFP_KERNEL);
         if (cd == NULL)
                 return ERR_PTR(-ENOMEM);