netdev - Re: [PATCH net] ipv4: Fix NULL pointer dereference in ipv4_neigh

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Date:   Fri, 05 Jul 2019 16:19:33 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     idosch@...sch.org
Cc:     netdev@...r.kernel.org, dsahern@...il.com, jiri@...lanox.com,
        shalomt@...lanox.com, mlxsw@...lanox.com, idosch@...lanox.com
Subject: Re: [PATCH net] ipv4: Fix NULL pointer dereference in
 ipv4_neigh_lookup()

From: Ido Schimmel <idosch@...sch.org>
Date: Thu,  4 Jul 2019 19:26:38 +0300

> From: Ido Schimmel <idosch@...lanox.com>
> 
> Both ip_neigh_gw4() and ip_neigh_gw6() can return either a valid pointer
> or an error pointer, but the code currently checks that the pointer is
> not NULL.
> 
> Fix this by checking that the pointer is not an error pointer, as this
> can result in a NULL pointer dereference [1]. Specifically, I believe
> that what happened is that ip_neigh_gw4() returned '-EINVAL'
> (0xffffffffffffffea) to which the offset of 'refcnt' (0x70) was added,
> which resulted in the address 0x000000000000005a.
> 
> [1]
 ...
> Fixes: 5c9f7c1dfc2e ("ipv4: Add helpers for neigh lookup for nexthop")
> Signed-off-by: Ido Schimmel <idosch@...lanox.com>
> Reported-by: Shalom Toledo <shalomt@...lanox.com>
> Reviewed-by: Jiri Pirko <jiri@...lanox.com>

Applied, thanks.