irda: prevent heap corruption on invalid nickname

Invalid nicknames containing only spaces will result in an underflow in a memcpy size calculation, subsequently destroying the heap and panicking.

v2 also catches the case where the provided nickname is longer than the buffer size, which can result in controllable heap corruption.

---
 net/irda/irnet/irnet_ppp.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

index 7c567b8..2bb2beb 100644
@@ -105,6 +105,9 @@ irnet_ctrl_write(irnet_socket *	ap,
 	      while(isspace(start[length - 1]))
 		length--;
 
+	      DABORT(length < 5 || length > NICKNAME_MAX_LEN + 5,
+		     -EINVAL, CTRL_ERROR, "Invalid nickname.\n");
+
 	      /* Copy the name for later reuse */
 	      memcpy(ap->rname, start + 5, length - 5);
 	      ap->rname[length - 5] = '\0';

From: Dan Rosenberg <[email protected]>
Date: Sun, 20 Mar 2011 02:14:30 -0400

Applied.