linux-kernel - Re: [PATCH] ib_isert: prevent NULL pointer dereference in isert_login_recv

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Message-ID: <20170629082057.GA2037@Dell>
Date:   Thu, 29 Jun 2017 10:20:57 +0200
From:   Andrea Righi <righi.andrea@...il.com>
To:     Sagi Grimberg <sagi@...mberg.me>
Cc:     "Nicholas A. Bellinger" <nab@...ux-iscsi.org>,
        Robert LeBlanc <robert@...lancnet.us>,
        Sean Jenkins <sean@...terservers.com>,
        Doug Ledford <dledford@...hat.com>,
        Sean Hefty <sean.hefty@...el.com>,
        Hal Rosenstock <hal.rosenstock@...il.com>,
        linux-rdma <linux-rdma@...r.kernel.org>,
        target-devel <target-devel@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH] ib_isert: prevent NULL pointer dereference in
 isert_login_recv_done()

On Thu, Jun 29, 2017 at 08:36:51AM +0300, Sagi Grimberg wrote:
> 
> >Just tested this patch, I wasn't able to reproduce the NULL pointer
> >dereference or any other bugs, so this fix seems safe enough to me.
> >
> >Tested-by: Andrea Righi <righi.andrea@...il.com>
> 
> Can you test just the one liner fix below?
> 
> >>@@ -1452,7 +1452,7 @@
> >>  isert_login_recv_done(struct ib_cq *cq, struct ib_wc *wc)
> >>  {
> >>  	struct isert_conn *isert_conn = wc->qp->qp_context;
> >>-	struct ib_device *ib_dev = isert_conn->cm_id->device;
> >>+	struct ib_device *ib_dev = isert_conn->device->ib_device;
> >>  	if (unlikely(wc->status != IB_WC_SUCCESS)) {
> >>  		isert_print_wc(wc, "login recv");

I'll test also this one-liner fix as soon as I can.

But I can say that I'm pretty sure it will work as well, because all the
previous NULL pointer dereferences that we've got in the past happened
all 100% in isert_login_recv_done(). The other cases are probably a safe
precaution, but they can't really happen.

-Andrea