linux-kernel - Re: [PATCH v3 2/2] ubi: expose the volume CRC check skip flag

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Date:   Sun, 01 Jul 2018 22:50:41 +0200
From:   Richard Weinberger <richard@....at>
To:     Boris Brezillon <boris.brezillon@...tlin.com>
Cc:     Quentin Schulz <quentin.schulz@...tlin.com>, dedekind1@...il.com,
        dwmw2@...radead.org, computersforpeace@...il.com,
        marek.vasut@...il.com, linux-mtd@...ts.infradead.org,
        linux-kernel@...r.kernel.org, thomas.petazzoni@...tlin.com
Subject: Re: [PATCH v3 2/2] ubi: expose the volume CRC check skip flag

Am Sonntag, 1. Juli 2018, 22:33:47 CEST schrieb Boris Brezillon:
> On Sun, 01 Jul 2018 21:35:57 +0200
> Richard Weinberger <richard@....at> wrote:
> 
> > Quentin,
> > 
> > Am Donnerstag, 28. Juni 2018, 09:40:53 CEST schrieb Quentin Schulz:
> > > Now that we have the logic for skipping CRC check for static UBI volumes
> > > in the core, let's expose it to users.
> > > 
> > > This makes use of a padding byte in the volume description data
> > > structure as a flag. This flag only tell for now whether we should skip
> > > the CRC check of a volume.
> > > 
> > > This checks the UBI volume for which we are trying to skip the CRC check
> > > is static.
> > > 
> > > Suggested-by: Boris Brezillon <boris.brezillon@...tlin.com>
> > > Signed-off-by: Quentin Schulz <quentin.schulz@...tlin.com>
> > > Reviewed-by: Boris Brezillon <boris.brezillon@...tlin.com>
> > > ---
> > >  drivers/mtd/ubi/cdev.c      |  4 ++++
> > >  drivers/mtd/ubi/vmt.c       |  3 +++
> > >  include/uapi/mtd/ubi-user.h | 16 ++++++++++++++--
> > >  3 files changed, 21 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/mtd/ubi/cdev.c b/drivers/mtd/ubi/cdev.c
> > > index 45c3296..3eea1df 100644
> > > --- a/drivers/mtd/ubi/cdev.c
> > > +++ b/drivers/mtd/ubi/cdev.c
> > > @@ -622,6 +622,10 @@ static int verify_mkvol_req(const struct ubi_device *ubi,
> > >  	    req->vol_type != UBI_STATIC_VOLUME)
> > >  		goto bad;
> > >  
> > > +	if (req->flags & UBI_VOL_SKIP_CRC_CHECK_FLG &&
> 
> Oops, missed that req->flags & UBI_VOL_SKIP_CRC_CHECK_FLG check was
> missing parens (checkpatch --strict should complain about that).

Latest when building my local branch or in linux-next we had noticed.
No need to worry.
 
> > > +	    req->vol_type != UBI_STATIC_VOLUME)
> > > +		goto bad;  
> > 
> > We should also reject unknown flags here.
> 
> I agree. Talking about missing checks, it seems that none of the
> padding sections are checked (I hope all mkvol users are zero-ing the
> struct as requested in ubi-user.h). And we should probably also
> check that vtbl->flags does not contain unknown flags.

At least mtd-utils does zeros the request struct before using it.
So it does the right thing.

Adding checks for non-zero padding and more checking for vtbl->flags
is a good idea.

Thanks,
//richard