net: fix info leak in compat dev_ifconf()

[ Upstream commit 43da5f2e0d0c69ded3d51907d9552310a6b545e8 ]

The implementation of dev_ifconf() for the compat ioctl interface uses
an intermediate ifc structure allocated in userland for the duration of
the syscall. Though, it fails to initialize the padding bytes inserted
for alignment and that for leaks four bytes of kernel stack. Add an
explicit memset(0) before filling the structure to avoid the info leak.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/socket.c b/net/socket.c
index a990aa97f257e9641249a326e18f66f84f9552c4..bce45cca6f67202e2bde011eb045cd2b35df4654 100644 (file)
--- a/net/socket.c
+++ b/net/socket.c
@@ -2658,6 +2658,7 @@ static int dev_ifconf(struct net *net, struct compat_ifconf __user *uifc32)
        if (copy_from_user(&ifc32, uifc32, sizeof(struct compat_ifconf)))
                return -EFAULT;
 
+       memset(&ifc, 0, sizeof(ifc));
        if (ifc32.ifcbuf == 0) {
                ifc32.ifc_len = 0;
                ifc.ifc_len = 0;