[NET]: Fix memory leak in sys_{send,recv}msg() w/compat

From: Dave Johnson <djohnson+linux-kernel@sw.starentnetworks.com>

sendmsg()/recvmsg() syscalls from o32/n32 apps to a 64bit kernel will
cause a kernel memory leak if iov_len > UIO_FASTIOV for each syscall!

This is because both sys_sendmsg() and verify_compat_iovec() kmalloc a
new iovec structure.  Only the one from sys_sendmsg() is free'ed.

I wrote a simple test program to confirm this after identifying the
problem:

http://davej.org/programs/testsendmsg.c

Note that the below fix will break solaris_sendmsg()/solaris_recvmsg() as
it also calls verify_compat_iovec() but expects it to malloc internally.

[ I fixed that. -DaveM ]

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 0 insertions, 9 deletions

diff --git a/net/compat.c b/net/compat.c
index be5d936dc423..d99ab9695893 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -91,20 +91,11 @@ int verify_compat_iovec(struct msghdr *kern_msg, struct iovec *kern_iov,
         } else
                 kern_msg->msg_name = NULL;
 
-        if(kern_msg->msg_iovlen > UIO_FASTIOV) {
-                kern_iov = kmalloc(kern_msg->msg_iovlen * sizeof(struct iovec),
-                                   GFP_KERNEL);
-                if(!kern_iov)
-                        return -ENOMEM;
-        }
-
         tot_len = iov_from_user_compat_to_kern(kern_iov,
                                           (struct compat_iovec __user *)kern_msg->msg_iov,
                                           kern_msg->msg_iovlen);
         if(tot_len >= 0)
                 kern_msg->msg_iov = kern_iov;
-        else if(kern_msg->msg_iovlen > UIO_FASTIOV)
-                kfree(kern_iov);
 
         return tot_len;
 }