[PATCH v2] irda: prevent heap corruption on invalid nickname

[Dan Rosenberg <drosenberg@vsecurity.com>]

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.

Signed-off-by: Dan Rosenberg <drosenberg@vsecurity.com>
Cc: stable@kernel.org
---
 net/irda/irnet/irnet_ppp.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/net/irda/irnet/irnet_ppp.c b/net/irda/irnet/irnet_ppp.c
index 7c567b8..2bb2beb 100644
--- a/net/irda/irnet/irnet_ppp.c
+++ b/net/irda/irnet/irnet_ppp.c
@@ -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';