[PATCH v3 2/4] chardev: add a check for given minor range

[Chengguang Xu]

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@xxxxxxx>
---
v1->v2:
- Split fix and cleanup patches.
- Remove printing minor range in chrdev_show().

 fs/char_dev.c | 6 ++++++
 1 file changed, 6 insertions(+)

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);
--
2.20.1