[PATCH] Fix kfree bug in sendmsg and recvmsg

[Joe Korty <joe.korty@ccur.com>]

Fix kfree bug in recvmsg and sendmsg.

We cannot kfree(iov) when iov points to an array on the
stack, as that has the potential of corrupting memory.

So re-introduce the if-stmt that used to protect kfree
from this condition, code that was removed as part of
a larger set of changes made by git commit da184284.

Signed-off-by: Joe Korty <joe.korty@ccur.com>

Index: b/net/socket.c
===================================================================
--- a/net/socket.c
+++ b/net/socket.c
@@ -1960,7 +1960,8 @@ out_freectl:
 	if (ctl_buf != ctl)
 		sock_kfree_s(sock->sk, ctl_buf, ctl_len);
 out_freeiov:
-	kfree(iov);
+	if (iov != iovstack)
+		kfree(iov);
 	return err;
 }
 
@@ -2125,7 +2126,8 @@ static int ___sys_recvmsg(struct socket 
 	err = len;
 
 out_freeiov:
-	kfree(iov);
+	if (iov != iovstack)
+		kfree(iov);
 	return err;
 }