Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752126AbcL1XmS (ORCPT ); Wed, 28 Dec 2016 18:42:18 -0500 Received: from fllnx210.ext.ti.com ([198.47.19.17]:54073 "EHLO fllnx210.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751890AbcL1XmR (ORCPT ); Wed, 28 Dec 2016 18:42:17 -0500 From: Grygorii Strashko To: "David S. Miller" , , Mugunthan V N CC: Sekhar Nori , , , Ivan Khoronzhuk , Grygorii Strashko Subject: [PATCH] net: ethernet: ti: davinci_cpdma: fix access to uninitialized variable in cpdma_chan_set_descs() Date: Wed, 28 Dec 2016 17:42:13 -0600 Message-ID: <20161228234213.22166-1-grygorii.strashko@ti.com> X-Mailer: git-send-email 2.10.1.dirty MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1657 Lines: 61 Now below code sequence causes "Unable to handle kernel NULL pointer dereference.." exception and system crash during CPSW CPDMA initialization: cpsw_probe |-cpdma_chan_create (TX channel) |-cpdma_chan_split_pool |-cpdma_chan_set_descs(for TX channels) |-cpdma_chan_set_descs(for RX channels) [1] - and - static void cpdma_chan_set_descs(struct cpdma_ctlr *ctlr, int rx, int desc_num, int per_ch_desc) { struct cpdma_chan *chan, *most_chan = NULL; ... for (i = min; i < max; i++) { chan = ctlr->channels[i]; if (!chan) continue; ... if (most_dnum < chan->desc_num) { most_dnum = chan->desc_num; most_chan = chan; } } /* use remains */ most_chan->desc_num += desc_cnt; [2] } So, most_chan value will never be reassigned when cpdma_chan_set_descs() is called second time [1], because there are no RX channels yet and system will crash at [2]. Hence, fix the issue by checking most_chan for NULL before accessing it. Fixes: 0fc6432cc78d ("net: ethernet: ti: davinci_cpdma: add weight function for channels") Signed-off-by: Grygorii Strashko --- drivers/net/ethernet/ti/davinci_cpdma.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/net/ethernet/ti/davinci_cpdma.c b/drivers/net/ethernet/ti/davinci_cpdma.c index 36518fc..b349d572 100644 --- a/drivers/net/ethernet/ti/davinci_cpdma.c +++ b/drivers/net/ethernet/ti/davinci_cpdma.c @@ -708,7 +708,8 @@ static void cpdma_chan_set_descs(struct cpdma_ctlr *ctlr, } } /* use remains */ - most_chan->desc_num += desc_cnt; + if (most_chan) + most_chan->desc_num += desc_cnt; } /** -- 2.10.1.dirty