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From: Ross Zwisler <ross.zwisler@linux.intel.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Colin King <colin.king@canonical.com>,
	kernel-janitors@vger.kernel.org,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-nvdimm@lists.01.org
Subject: Re: [PATCH] libnvdimm: remove redundant assignment to pointer 'dev'
Date: Mon, 05 Feb 2018 21:35:44 +0000	[thread overview]
Message-ID: <20180205213544.GA30855@linux.intel.com> (raw)
In-Reply-To: <CAPcyv4geaysZ803Xtd27YGh0udww+95VaGP6r1Hdxx8SHxfX9w@mail.gmail.com>

On Mon, Feb 05, 2018 at 10:44:07AM -0800, Dan Williams wrote:
> On Mon, Feb 5, 2018 at 10:20 AM, Ross Zwisler
> <ross.zwisler@linux.intel.com> wrote:
> > On Mon, Feb 05, 2018 at 02:08:52PM +0000, Colin King wrote:
> >> From: Colin Ian King <colin.king@canonical.com>
> >>
> >> Pointer dev is being assigned a value that is never read, it is being
> >> re-assigned the same value later on, hence the initialization is redundant
> >> and can be removed.
> >>
> >> Cleans up clang warning:
> >> drivers/nvdimm/pfn_devs.c:307:17: warning: Value stored to 'dev' during
> >> its initialization is never read
> >>
> >> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> >
> > Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> >
> > More importantly this fixes a potential NULL pointer dereference.  nd_pfn
> > is checked for NULL a few lines down, but we would have crashed here trying to
> > get nd_pfn->dev.
> >
> 
> No we wouldn't crash. We're just calculating the address, not
> de-referencing a NULL pointer.

Ah, yep, you're right of course.  This is exactly how offsetof() is
implemented in some architectures.  Thanks.

WARNING: multiple messages have this Message-ID (diff)
From: Ross Zwisler <ross.zwisler@linux.intel.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Colin King <colin.king@canonical.com>,
	kernel-janitors@vger.kernel.org,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-nvdimm@lists.01.org
Subject: Re: [PATCH] libnvdimm: remove redundant assignment to pointer 'dev'
Date: Mon, 5 Feb 2018 14:35:44 -0700	[thread overview]
Message-ID: <20180205213544.GA30855@linux.intel.com> (raw)
In-Reply-To: <CAPcyv4geaysZ803Xtd27YGh0udww+95VaGP6r1Hdxx8SHxfX9w@mail.gmail.com>

On Mon, Feb 05, 2018 at 10:44:07AM -0800, Dan Williams wrote:
> On Mon, Feb 5, 2018 at 10:20 AM, Ross Zwisler
> <ross.zwisler@linux.intel.com> wrote:
> > On Mon, Feb 05, 2018 at 02:08:52PM +0000, Colin King wrote:
> >> From: Colin Ian King <colin.king@canonical.com>
> >>
> >> Pointer dev is being assigned a value that is never read, it is being
> >> re-assigned the same value later on, hence the initialization is redundant
> >> and can be removed.
> >>
> >> Cleans up clang warning:
> >> drivers/nvdimm/pfn_devs.c:307:17: warning: Value stored to 'dev' during
> >> its initialization is never read
> >>
> >> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> >
> > Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> >
> > More importantly this fixes a potential NULL pointer dereference.  nd_pfn
> > is checked for NULL a few lines down, but we would have crashed here trying to
> > get nd_pfn->dev.
> >
> 
> No we wouldn't crash. We're just calculating the address, not
> de-referencing a NULL pointer.

Ah, yep, you're right of course.  This is exactly how offsetof() is
implemented in some architectures.  Thanks.
_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm

WARNING: multiple messages have this Message-ID (diff)
From: Ross Zwisler <ross.zwisler@linux.intel.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>,
	Colin King <colin.king@canonical.com>,
	linux-nvdimm@lists.01.org, kernel-janitors@vger.kernel.org,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] libnvdimm: remove redundant assignment to pointer 'dev'
Date: Mon, 5 Feb 2018 14:35:44 -0700	[thread overview]
Message-ID: <20180205213544.GA30855@linux.intel.com> (raw)
In-Reply-To: <CAPcyv4geaysZ803Xtd27YGh0udww+95VaGP6r1Hdxx8SHxfX9w@mail.gmail.com>

On Mon, Feb 05, 2018 at 10:44:07AM -0800, Dan Williams wrote:
> On Mon, Feb 5, 2018 at 10:20 AM, Ross Zwisler
> <ross.zwisler@linux.intel.com> wrote:
> > On Mon, Feb 05, 2018 at 02:08:52PM +0000, Colin King wrote:
> >> From: Colin Ian King <colin.king@canonical.com>
> >>
> >> Pointer dev is being assigned a value that is never read, it is being
> >> re-assigned the same value later on, hence the initialization is redundant
> >> and can be removed.
> >>
> >> Cleans up clang warning:
> >> drivers/nvdimm/pfn_devs.c:307:17: warning: Value stored to 'dev' during
> >> its initialization is never read
> >>
> >> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> >
> > Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> >
> > More importantly this fixes a potential NULL pointer dereference.  nd_pfn
> > is checked for NULL a few lines down, but we would have crashed here trying to
> > get nd_pfn->dev.
> >
> 
> No we wouldn't crash. We're just calculating the address, not
> de-referencing a NULL pointer.

Ah, yep, you're right of course.  This is exactly how offsetof() is
implemented in some architectures.  Thanks.

  parent reply	other threads:[~2018-02-05 21:35 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-05 14:08 [PATCH] libnvdimm: remove redundant assignment to pointer 'dev' Colin King
2018-02-05 14:08 ` Colin King
2018-02-05 14:08 ` Colin King
2018-02-05 18:20 ` Ross Zwisler
2018-02-05 18:20   ` Ross Zwisler
2018-02-05 18:20   ` Ross Zwisler
2018-02-05 18:44   ` Dan Williams
2018-02-05 18:44     ` Dan Williams
2018-02-05 18:44     ` Dan Williams
2018-02-05 20:46     ` Colin Ian King
2018-02-05 20:46       ` Colin Ian King
2018-02-05 20:46       ` Colin Ian King
2018-02-05 21:35     ` Ross Zwisler [this message]
2018-02-05 21:35       ` Ross Zwisler
2018-02-05 21:35       ` Ross Zwisler

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