linux-kernel - Re: [PATCH -next] mtd: ubi: wl: Fix error return code in ubi_wl

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Date:   Thu, 18 Jan 2018 15:11:32 +0100
From:   Boris Brezillon <boris.brezillon@...e-electrons.com>
To:     Wei Yongjun <weiyongjun1@...wei.com>
Cc:     Artem Bityutskiy <dedekind1@...il.com>,
        Richard Weinberger <richard@....at>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Cyrille Pitchen <cyrille.pitchen@...ev4u.fr>,
        <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <kernel-janitors@...r.kernel.org>
Subject: Re: [PATCH -next] mtd: ubi: wl: Fix error return code in
 ubi_wl_init()

On Thu, 18 Jan 2018 15:08:01 +0100
Boris Brezillon <boris.brezillon@...e-electrons.com> wrote:

> On Thu, 18 Jan 2018 14:05:05 +0000
> Wei Yongjun <weiyongjun1@...wei.com> wrote:
> 
> > Fix to return error code -ENOMEM from the kmem_cache_alloc() error
> > handling case instead of 0, as done elsewhere in this function.  
> 
> I guess you've used a static analysis code to detect this problem, can
> you name it in the commit message, and paste the error/warning message
> it reported next time you submit this kind of patch.
> 
> > 
> > Signed-off-by: Wei Yongjun <weiyongjun1@...wei.com>  
> 
> NAck. I you read the code you'll see that err is initialized to -ENOMEM
> here [1], so these changes are actually not needed.

Sorry, just realized I was wrong. It seems that err can be overridden by
[2]. So this patch is indeed fixing a real problem.

Reviewed-by: Boris Brezillon <boris.brezillon@...e-electrons.com>

> 
> > ---
> >  drivers/mtd/ubi/wl.c | 8 ++++++--
> >  1 file changed, 6 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
> > index 77ab49f..2052a64 100644
> > --- a/drivers/mtd/ubi/wl.c
> > +++ b/drivers/mtd/ubi/wl.c
> > @@ -1617,8 +1617,10 @@ int ubi_wl_init(struct ubi_device *ubi, struct ubi_attach_info *ai)
> >  		cond_resched();
> >  
> >  		e = kmem_cache_alloc(ubi_wl_entry_slab, GFP_KERNEL);
> > -		if (!e)
> > +		if (!e) {
> > +			err = -ENOMEM;
> >  			goto out_free;
> > +		}
> >  
> >  		e->pnum = aeb->pnum;
> >  		e->ec = aeb->ec;
> > @@ -1637,8 +1639,10 @@ int ubi_wl_init(struct ubi_device *ubi, struct ubi_attach_info *ai)
> >  			cond_resched();
> >  
> >  			e = kmem_cache_alloc(ubi_wl_entry_slab, GFP_KERNEL);
> > -			if (!e)
> > +			if (!e) {
> > +				err = -ENOMEM;
> >  				goto out_free;
> > +			}
> >  
> >  			e->pnum = aeb->pnum;
> >  			e->ec = aeb->ec;
> >   
> 
> [1]https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/mtd/ubi/wl.c?h=next-20180118#n1596

[2]https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/mtd/ubi/wl.c?h=next-20180118#n1609