Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932586Ab3J1PJl (ORCPT ); Mon, 28 Oct 2013 11:09:41 -0400 Received: from mail-ie0-f169.google.com ([209.85.223.169]:33492 "EHLO mail-ie0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932470Ab3J1PJh (ORCPT ); Mon, 28 Oct 2013 11:09:37 -0400 MIME-Version: 1.0 In-Reply-To: References: <20131019110539.GA25167@gmail.com> Date: Mon, 28 Oct 2013 23:09:36 +0800 Message-ID: Subject: Re: [PATCH v6 1/3] Staging: zram: Fix access of NULL pointer From: Weijie Yang To: Rashika Kheria Cc: opw-kernel , Greg Kroah-Hartman , Minchan Kim , Jiang Liu , Nitin Gupta , Jerome Marchand , Linux-Kernel Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1890 Lines: 63 On Mon, Oct 28, 2013 at 10:33 PM, Rashika Kheria wrote: > > > > On Mon, Oct 28, 2013 at 7:15 PM, Weijie Yang > wrote: >> >> On Mon, Oct 28, 2013 at 8:21 PM, Rashika Kheria >> wrote: >> > This patch fixes the bug in reset_store caused by accessing NULL >> > pointer. >> > Hence, It introduces a check for bdev. It also removes unnecessary check >> > of bdev for fsync_bdev(). >> > >> > Signed-off-by: Rashika Kheria >> > --- >> > >> > This revision fixes the following issues of the previous revision- >> > Seperating patches into Bug fix and Smatch fix >> > >> > drivers/staging/zram/zram_drv.c | 6 ++++-- >> > 1 file changed, 4 insertions(+), 2 deletions(-) >> > >> > diff --git a/drivers/staging/zram/zram_drv.c >> > b/drivers/staging/zram/zram_drv.c >> > index 2c4ed52..d640a8f 100644 >> > --- a/drivers/staging/zram/zram_drv.c >> > +++ b/drivers/staging/zram/zram_drv.c >> > @@ -648,6 +648,9 @@ static ssize_t reset_store(struct device *dev, >> > zram = dev_to_zram(dev); >> > bdev = bdget_disk(zram->disk, 0); >> > >> > + if (!bdev) >> > + return -EBUSY; >> > + >> >> I am not sure how does it happen. Would you please make it clear to me? >> > > Hi Weijie, > > The bdev gets its value from bdget_disk() which could fail when memory is > less available and hence bdev can be NULL. > > If this check is not introduced then we might reference NULL pointer in the > later part of the code. I see. Thanks! > I hope I am clear. > > Thanks, > > -- > Rashika Kheria > B.Tech CSE > IIIT Hyderabad -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/