Re: [PATCH] net: mark DECnet as broken

From: David Miller
Date: Sun Apr 10 2016 - 23:02:14 EST


From: Vegard Nossum <vegard.nossum@xxxxxxxxxx>
Date: Thu, 7 Apr 2016 09:22:43 +0200

> There are NULL pointer dereference bugs in DECnet which can be triggered
> by unprivileged users and have been reported multiple times to LKML,
> however nobody seems confident enough in the proposed fixes to merge them
> and the consensus seems to be that nobody cares enough about DECnet to
> see it fixed anyway.
>
> To shield unsuspecting users from the possible DOS, we should mark this
> BROKEN until somebody who actually uses this code can fix it.
>
> Signed-off-by: Vegard Nossum <vegard.nossum@xxxxxxxxxx>
> Link: https://lkml.org/lkml/2015/12/17/666

As stated, I'm not applying this, and rather I am fixing this as
below:

====================
[PATCH] decnet: Do not build routes to devices without decnet private data.

In particular, make sure we check for decnet private presence
for loopback devices.

Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
---
net/decnet/dn_route.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/net/decnet/dn_route.c b/net/decnet/dn_route.c
index 607a14f..b1dc096 100644
--- a/net/decnet/dn_route.c
+++ b/net/decnet/dn_route.c
@@ -1034,10 +1034,13 @@ source_ok:
if (!fld.daddr) {
fld.daddr = fld.saddr;

- err = -EADDRNOTAVAIL;
if (dev_out)
dev_put(dev_out);
+ err = -EINVAL;
dev_out = init_net.loopback_dev;
+ if (!dev_out->dn_ptr)
+ goto out;
+ err = -EADDRNOTAVAIL;
dev_hold(dev_out);
if (!fld.daddr) {
fld.daddr =
@@ -1110,6 +1113,8 @@ source_ok:
if (dev_out == NULL)
goto out;
dn_db = rcu_dereference_raw(dev_out->dn_ptr);
+ if (!dn_db)
+ goto e_inval;
/* Possible improvement - check all devices for local addr */
if (dn_dev_islocal(dev_out, fld.daddr)) {
dev_put(dev_out);
@@ -1151,6 +1156,8 @@ select_source:
dev_put(dev_out);
dev_out = init_net.loopback_dev;
dev_hold(dev_out);
+ if (!dev_out->dn_ptr)
+ goto e_inval;
fld.flowidn_oif = dev_out->ifindex;
if (res.fi)
dn_fib_info_put(res.fi);
--
2.1.0