Re: [PATCH] can: check for null sk before deferencing it via the call to sock_net

On Fri, Sep 8, 2017 at 1:46 PM, Oliver Hartkopp [off-list ref] wrote:

On 09/08/2017 05:02 PM, Colin King wrote:

quoted

From: Colin Ian King <redacted>

The assignment of net via call sock_net will dereference sk. This
is performed before a sanity null check on sk, so there could be
a potential null dereference on the sock_net call if sk is null.
Fix this by assigning net after the sk null check. Also replace
the sk == NULL with the more usual !sk idiom.

Detected by CoverityScan CID#1431862 ("Dereference before null check")

Fixes: 384317ef4187 ("can: network namespace support for CAN_BCM
protocol")
Signed-off-by: Colin Ian King <redacted>

Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>

I don't see this one queued up in the net or net-next trees.  Did it
fall through the cracks or did it get queued up elsewhere?  Seems like
it's a good candidate to get into 4.14?

josh

Thanks Collin!

quoted

---
  net/can/bcm.c | 5 +++--
  1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/can/bcm.c b/net/can/bcm.c
index 47a8748d953a..a3791674b8ce 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c

@@ -1493,13 +1493,14 @@ static int bcm_init(struct sock *sk)
  static int bcm_release(struct socket *sock)
  {
        struct sock *sk = sock->sk;
-       struct net *net = sock_net(sk);
+       struct net *net;
        struct bcm_sock *bo;
        struct bcm_op *op, *next;
  -     if (sk == NULL)
+       if (!sk)
                return 0;
  +     net = sock_net(sk);
        bo = bcm_sk(sk);
        /* remove bcm_ops, timer, rx_unregister(), etc. */