linux-kernel - Re: [PATCH 1/1] mtd: ubi: fix improper return value

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Date:   Sun, 04 Dec 2016 12:33:39 -0800
From:   Joe Perches <joe@...ches.com>
To:     Marek Vasut <marek.vasut@...il.com>,
        Pan Bian <bianpan201604@....com>,
        Artem Bityutskiy <dedekind1@...il.com>,
        Richard Weinberger <richard@....at>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Cyrille Pitchen <cyrille.pitchen@...el.com>,
        linux-mtd@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, Pan Bian <bianpan2016@....com>
Subject: Re: [PATCH 1/1] mtd: ubi: fix improper return value

On Sun, 2016-12-04 at 13:48 +0100, Marek Vasut wrote:
> On 12/04/2016 07:12 AM, Pan Bian wrote:
> > From: Pan Bian <bianpan2016@....com>
> > 
> > When __vmalloc() returns a NULL pointer, the region is not checked, and
> > we cannot make sure that only 0xFF bytes are present at offset. Thus,
> > returning 0 seems improper.
> > 
> > Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=189081
> > 
> > Signed-off-by: Pan Bian <bianpan2016@....com>
> > ---
> >  drivers/mtd/ubi/io.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/mtd/ubi/io.c b/drivers/mtd/ubi/io.c
[]
> > @@ -1413,7 +1413,7 @@ int ubi_self_check_all_ff(struct ubi_device *ubi, int pnum, int offset, int len)
> >  	buf = __vmalloc(len, GFP_NOFS, PAGE_KERNEL);
> >  	if (!buf) {
> >  		ubi_err(ubi, "cannot allocate memory to check for 0xFFs");
> > -		return 0;
> > +		return -ENOMEM;
> 
> I wonder if you shouldn't also nuke the ubi_err() , because when you run
> out of memory, printk() will likely also fail.

No, not really.  printk doesn't allocate memory.

But the ubi_err should be removed because all memory
allocations that fail without a specific GFP_NOWARN
flag already have a dump_stack() call.