From: Dan Carpenter <dan.carpenter@oracle.com>
To: Mike Snitzer <snitzer@redhat.com>
Cc: Alasdair Kergon <agk@redhat.com>,
dm-devel@redhat.com, Neil Brown <neilb@suse.de>,
linux-raid@vger.kernel.org, kernel-janitors@vger.kernel.org,
Heinz Mauelshagen <heinzm@redhat.com>
Subject: Re: dm raid: pointer math issue in super_sync()
Date: Tue, 21 Oct 2014 15:57:29 +0300 [thread overview]
Message-ID: <20141021125729.GC26918@mwanda> (raw)
In-Reply-To: <20141021124826.GC20625@redhat.com>
On Tue, Oct 21, 2014 at 08:48:26AM -0400, Mike Snitzer wrote:
> > - memset(sb + sizeof(*sb), 0, rdev->sb_size - sizeof(*sb));
> > + memset(sb + 1, 0, rdev->sb_size - sizeof(*sb));
> >
> > sb->magic = cpu_to_le32(DM_RAID_MAGIC);
> > sb->features = cpu_to_le32(0); /* No features yet */
>
> Not following... sizeof(*sb) != sizeof(sb). So I'm not seeing a
> problem.
>
> Nor am I seeing how you think sb + 1 is equivalent to what Heinz
> intended (zero the memory following the sizeof(struct dm_raid_superblock)).
It's pointer math.
sizeof(*sb) is 512.
"sb + sizeof(*sb)" is the same as (void *)sb + 512 * 512.
"sb + 1" is the same as (void *)sb + 512.
regards,
dan carpenter
WARNING: multiple messages have this Message-ID (diff)
From: Dan Carpenter <dan.carpenter@oracle.com>
To: Mike Snitzer <snitzer@redhat.com>
Cc: Alasdair Kergon <agk@redhat.com>,
dm-devel@redhat.com, Neil Brown <neilb@suse.de>,
linux-raid@vger.kernel.org, kernel-janitors@vger.kernel.org,
Heinz Mauelshagen <heinzm@redhat.com>
Subject: Re: dm raid: pointer math issue in super_sync()
Date: Tue, 21 Oct 2014 12:57:29 +0000 [thread overview]
Message-ID: <20141021125729.GC26918@mwanda> (raw)
In-Reply-To: <20141021124826.GC20625@redhat.com>
On Tue, Oct 21, 2014 at 08:48:26AM -0400, Mike Snitzer wrote:
> > - memset(sb + sizeof(*sb), 0, rdev->sb_size - sizeof(*sb));
> > + memset(sb + 1, 0, rdev->sb_size - sizeof(*sb));
> >
> > sb->magic = cpu_to_le32(DM_RAID_MAGIC);
> > sb->features = cpu_to_le32(0); /* No features yet */
>
> Not following... sizeof(*sb) != sizeof(sb). So I'm not seeing a
> problem.
>
> Nor am I seeing how you think sb + 1 is equivalent to what Heinz
> intended (zero the memory following the sizeof(struct dm_raid_superblock)).
It's pointer math.
sizeof(*sb) is 512.
"sb + sizeof(*sb)" is the same as (void *)sb + 512 * 512.
"sb + 1" is the same as (void *)sb + 512.
regards,
dan carpenter
next prev parent reply other threads:[~2014-10-21 12:57 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-21 12:43 [patch] dm raid: pointer math issue in super_sync() Dan Carpenter
2014-10-21 12:43 ` Dan Carpenter
2014-10-21 12:48 ` Mike Snitzer
2014-10-21 12:48 ` Mike Snitzer
2014-10-21 12:57 ` Dan Carpenter [this message]
2014-10-21 12:57 ` Dan Carpenter
2014-10-21 13:25 ` Mike Snitzer
2014-10-21 13:25 ` Mike Snitzer
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