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authorJan Kara <jack@suse.cz>2015-06-02 12:38:39 +0200
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2015-06-15 10:51:12 +0200
commit8cb81811e924ff0214ce4e8344e2feb1549cf0ce (patch)
tree4bb8a52ff2121d335f893ad2d2cf4bfa89e47ece
parent2e4aa2f2bdcf9b80bace0b0c460bd407d76f49d3 (diff)
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: Jan Kara <jack@suse.cz> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
-rw-r--r--drivers/s390/char/keyboard.c13
1 files changed, 8 insertions, 5 deletions
diff --git a/drivers/s390/char/keyboard.c b/drivers/s390/char/keyboard.c
index 01463b052ae7..ef04a9f7a704 100644
--- a/drivers/s390/char/keyboard.c
+++ b/drivers/s390/char/keyboard.c
@@ -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;