irda: prevent integer underflow in IRLMP_ENUMDEVICES
If the user-provided len is less than the expected offset, the
IRLMP_ENUMDEVICES getsockopt will do a copy_to_user() with a very large
size value. While this isn't be a security issue on x86 because it will
get caught by the access_ok() check, it may leak large amounts of kernel
heap on other architectures. In any event, this patch fixes it.
Signed-off-by: Dan Rosenberg <drosenberg@vsecurity.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/irda/af_irda.c b/net/irda/af_irda.c
index 7f097989..5007541 100644
--- a/net/irda/af_irda.c
+++ b/net/irda/af_irda.c
@@ -2281,6 +2281,16 @@
switch (optname) {
case IRLMP_ENUMDEVICES:
+
+ /* Offset to first device entry */
+ offset = sizeof(struct irda_device_list) -
+ sizeof(struct irda_device_info);
+
+ if (len < offset) {
+ err = -EINVAL;
+ goto out;
+ }
+
/* Ask lmp for the current discovery log */
discoveries = irlmp_get_discoveries(&list.len, self->mask.word,
self->nslots);
@@ -2291,15 +2301,9 @@
}
/* Write total list length back to client */
- if (copy_to_user(optval, &list,
- sizeof(struct irda_device_list) -
- sizeof(struct irda_device_info)))
+ if (copy_to_user(optval, &list, offset))
err = -EFAULT;
- /* Offset to first device entry */
- offset = sizeof(struct irda_device_list) -
- sizeof(struct irda_device_info);
-
/* Copy the list itself - watch for overflow */
if (list.len > 2048) {
err = -EINVAL;