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Commit 8cb81811 authored by Jan Kara's avatar Jan Kara Committed by Martin Schwidefsky
Browse files

s390/keyboard: avoid off-by-one when using strnlen_user() 



strnlen_user() returns the length of the string including terminating 0.
So avoid counting it again and unnecessarily reducing maximum string
size by 1.

Signed-off-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 2e4aa2f2

drivers/s390/char/keyboard.c

+8 −5
Original line number Diff line number Diff line
@@ -433,20 +433,23 @@ do_kdgkb_ioctl(struct kbd_data *kbd, struct kbsentry __user *u_kbs, 
	case KDSKBSENT:

		if (!perm)

			return -EPERM;

		len = strnlen_user(u_kbs->kb_string,

				   sizeof(u_kbs->kb_string) - 1);

		len = strnlen_user(u_kbs->kb_string, sizeof(u_kbs->kb_string));

		if (!len)

			return -EFAULT;

		if (len > sizeof(u_kbs->kb_string) - 1)

		if (len > sizeof(u_kbs->kb_string))

			return -EINVAL;

		p = kmalloc(len + 1, GFP_KERNEL);

		p = kmalloc(len, GFP_KERNEL);

		if (!p)

			return -ENOMEM;

		if (copy_from_user(p, u_kbs->kb_string, len)) {

			kfree(p);

			return -EFAULT;

		}

		p[len] = 0;

		/*

		 * Make sure the string is terminated by 0. User could have

		 * modified it between us running strnlen_user() and copying it.

		 */

		p[len - 1] = 0;

		kfree(kbd->func_table[kb_func]);

		kbd->func_table[kb_func] = p;

		break;