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Date: Mon, 28 Oct 2013 23:09:36 +0800 From: Weijie Yang <weijie.yang.kh@...il.com> To: Rashika Kheria <rashika.kheria@...il.com> Cc: opw-kernel <opw-kernel@...glegroups.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Minchan Kim <minchan@...nel.org>, Jiang Liu <jiang.liu@...wei.com>, Nitin Gupta <ngupta@...are.org>, Jerome Marchand <jmarchand@...hat.com>, Linux-Kernel <linux-kernel@...r.kernel.org> Subject: Re: [PATCH v6 1/3] Staging: zram: Fix access of NULL pointer On Mon, Oct 28, 2013 at 10:33 PM, Rashika Kheria <rashika.kheria@...il.com> wrote: > > > > On Mon, Oct 28, 2013 at 7:15 PM, Weijie Yang <weijie.yang.kh@...il.com> > wrote: >> >> On Mon, Oct 28, 2013 at 8:21 PM, Rashika Kheria >> <rashika.kheria@...il.com> 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 <rashika.kheria@...il.com> >> > --- >> > >> > 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@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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