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From: Christoph Hellwig <hch@lst.de>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>, Ian Abbott <abbotti@mev.co.uk>,
	Jiri Slaby <jslaby@suse.com>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Robin Murphy <robin.murphy@arm.com>,
	iommu@lists.linux-foundation.org,
	"kernel-janitors@vger.kernel.org H Hartley Sweeten"
	<hsweeten@visionengravers.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] dma-mapping: remove an unnecessary NULL check
Date: Wed, 24 Apr 2019 16:27:43 +0200	[thread overview]
Message-ID: <20190424142743.GC20974@lst.de> (raw)
In-Reply-To: <20190424142437.GA29490@mwanda>

On Wed, Apr 24, 2019 at 05:24:37PM +0300, Dan Carpenter wrote:
> We already dereferenced "dev" when we called get_dma_ops() so this NULL
> check is too late.  We're not supposed to pass NULL "dev" pointers to
> dma_alloc_attrs().

Thanks, applied to the dma-mapping for-next tree.

> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
> There are still at least two drivers which do pass a NULL unfortunately.
> 
> drivers/staging/comedi/drivers/comedi_isadma.c:195 comedi_isadma_alloc() error: NULL dereference inside function 'dma_alloc_coherent()'
> drivers/staging/comedi/drivers/comedi_isadma.c:227 comedi_isadma_free() error: NULL dereference inside function 'dma_free_coherent()'

This is staging code.  Per official decree from Linus we can just
ignore it, and I tend to do so to keep my sanity.

> drivers/tty/synclink.c:3667 mgsl_alloc_buffer_list_memory() error: NULL dereference inside function 'dma_alloc_coherent()'
> drivers/tty/synclink.c:3738 mgsl_free_buffer_list_memory() error: NULL dereference inside function 'dma_free_coherent()'
> drivers/tty/synclink.c:3777 mgsl_alloc_frame_memory() error: NULL dereference inside function 'dma_alloc_coherent()'
> drivers/tty/synclink.c:3811 mgsl_free_frame_memory() error: NULL dereference inside function 'dma_free_coherent()'

The !PCI case there is dead since I removed PCI support a while ago.
Looks like it is still too convoluted for static checkers to notice that,
though.

WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
	"kernel-janitors@vger.kernel.org H Hartley Sweeten"
	<hsweeten@visionengravers.com>, Ian Abbott <abbotti@mev.co.uk>,
	Jiri Slaby <jslaby@suse.com>, Robin Murphy <robin.murphy@arm.com>,
	Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH] dma-mapping: remove an unnecessary NULL check
Date: Wed, 24 Apr 2019 16:27:43 +0200	[thread overview]
Message-ID: <20190424142743.GC20974@lst.de> (raw)
Message-ID: <20190424142743.frqwdcu4dGOGzkPT4L1E5H16lJpzczOU9S0lDkDdlg8@z> (raw)
In-Reply-To: <20190424142437.GA29490@mwanda>

On Wed, Apr 24, 2019 at 05:24:37PM +0300, Dan Carpenter wrote:
> We already dereferenced "dev" when we called get_dma_ops() so this NULL
> check is too late.  We're not supposed to pass NULL "dev" pointers to
> dma_alloc_attrs().

Thanks, applied to the dma-mapping for-next tree.

> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
> There are still at least two drivers which do pass a NULL unfortunately.
> 
> drivers/staging/comedi/drivers/comedi_isadma.c:195 comedi_isadma_alloc() error: NULL dereference inside function 'dma_alloc_coherent()'
> drivers/staging/comedi/drivers/comedi_isadma.c:227 comedi_isadma_free() error: NULL dereference inside function 'dma_free_coherent()'

This is staging code.  Per official decree from Linus we can just
ignore it, and I tend to do so to keep my sanity.

> drivers/tty/synclink.c:3667 mgsl_alloc_buffer_list_memory() error: NULL dereference inside function 'dma_alloc_coherent()'
> drivers/tty/synclink.c:3738 mgsl_free_buffer_list_memory() error: NULL dereference inside function 'dma_free_coherent()'
> drivers/tty/synclink.c:3777 mgsl_alloc_frame_memory() error: NULL dereference inside function 'dma_alloc_coherent()'
> drivers/tty/synclink.c:3811 mgsl_free_frame_memory() error: NULL dereference inside function 'dma_free_coherent()'

The !PCI case there is dead since I removed PCI support a while ago.
Looks like it is still too convoluted for static checkers to notice that,
though.
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  reply	other threads:[~2019-04-24 14:27 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-24 14:24 [PATCH] dma-mapping: remove an unnecessary NULL check Dan Carpenter
2019-04-24 14:24 ` Dan Carpenter
2019-04-24 14:24 ` Dan Carpenter
2019-04-24 14:27 ` Christoph Hellwig [this message]
2019-04-24 14:27   ` Christoph Hellwig
2019-04-25 14:13   ` Ian Abbott
2019-04-25 14:13     ` Ian Abbott
2019-04-25 14:18     ` Christoph Hellwig
2019-04-25 14:18       ` Christoph Hellwig
2019-04-25 14:31       ` Ian Abbott
2019-04-25 14:31         ` Ian Abbott
2019-04-25 14:32         ` Christoph Hellwig
2019-04-25 14:32           ` Christoph Hellwig

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