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From: Christoph Hellwig <hch@infradead.org>
To: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: DRI Development <dri-devel@lists.freedesktop.org>,
	LKML <linux-kernel@vger.kernel.org>,
	kvm@vger.kernel.org, linux-mm@kvack.org,
	linux-arm-kernel@lists.infradead.org,
	linux-samsung-soc@vger.kernel.org, linux-media@vger.kernel.org,
	linux-s390@vger.kernel.org,
	Daniel Vetter <daniel.vetter@intel.com>,
	Jason Gunthorpe <jgg@ziepe.ca>, Kees Cook <keescook@chromium.org>,
	Dan Williams <dan.j.williams@intel.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	John Hubbard <jhubbard@nvidia.com>,
	J??r??me Glisse <jglisse@redhat.com>, Jan Kara <jack@suse.cz>
Subject: Re: [PATCH v4 08/15] mm: Add unsafe_follow_pfn
Date: Thu, 29 Oct 2020 08:56:44 +0000	[thread overview]
Message-ID: <20201029085644.GA25658@infradead.org> (raw)
In-Reply-To: <20201026105818.2585306-9-daniel.vetter@ffwll.ch>

> +int unsafe_follow_pfn(struct vm_area_struct *vma, unsigned long address,
> +	unsigned long *pfn)

The one tab indent here looks weird, normally tis would be two tabs
or aligned aftetthe opening brace.

> +{
> +#ifdef CONFIG_STRICT_FOLLOW_PFN
> +	pr_info("unsafe follow_pfn usage rejected, see CONFIG_STRICT_FOLLOW_PFN\n");
> +	return -EINVAL;
> +#else
> +	WARN_ONCE(1, "unsafe follow_pfn usage\n");
> +	add_taint(TAINT_USER, LOCKDEP_STILL_OK);
> +
> +	return follow_pfn(vma, address, pfn);
> +#endif

Woudn't this be a pretty good use case of "if (IS_ENABLED(...)))"?

Also I'd expect the inverse polarity of the config option, that is
a USAFE_FOLLOW_PFN option to enable to unsafe behavior.

> +/**
> + * unsafe_follow_pfn - look up PFN at a user virtual address
> + * @vma: memory mapping
> + * @address: user virtual address
> + * @pfn: location to store found PFN
> + *
> + * Only IO mappings and raw PFN mappings are allowed.
> + *
> + * Returns zero and the pfn at @pfn on success, -ve otherwise.
> + */
> +int unsafe_follow_pfn(struct vm_area_struct *vma, unsigned long address,
> +	unsigned long *pfn)
> +{
> +	return follow_pfn(vma, address, pfn);
> +}
> +EXPORT_SYMBOL(unsafe_follow_pfn);

Any reason this doesn't use the warn and disable logic?

WARNING: multiple messages have this Message-ID
From: Christoph Hellwig <hch@infradead.org>
To: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: linux-s390@vger.kernel.org, linux-samsung-soc@vger.kernel.org,
	Jan Kara <jack@suse.cz>, Kees Cook <keescook@chromium.org>,
	kvm@vger.kernel.org, Jason Gunthorpe <jgg@ziepe.ca>,
	John Hubbard <jhubbard@nvidia.com>,
	LKML <linux-kernel@vger.kernel.org>,
	DRI Development <dri-devel@lists.freedesktop.org>,
	linux-mm@kvack.org, J??r??me Glisse <jglisse@redhat.com>,
	Daniel Vetter <daniel.vetter@intel.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-arm-kernel@lists.infradead.org,
	linux-media@vger.kernel.org
Subject: Re: [PATCH v4 08/15] mm: Add unsafe_follow_pfn
Date: Thu, 29 Oct 2020 08:56:44 +0000	[thread overview]
Message-ID: <20201029085644.GA25658@infradead.org> (raw)
In-Reply-To: <20201026105818.2585306-9-daniel.vetter@ffwll.ch>

> +int unsafe_follow_pfn(struct vm_area_struct *vma, unsigned long address,
> +	unsigned long *pfn)

The one tab indent here looks weird, normally tis would be two tabs
or aligned aftetthe opening brace.

> +{
> +#ifdef CONFIG_STRICT_FOLLOW_PFN
> +	pr_info("unsafe follow_pfn usage rejected, see CONFIG_STRICT_FOLLOW_PFN\n");
> +	return -EINVAL;
> +#else
> +	WARN_ONCE(1, "unsafe follow_pfn usage\n");
> +	add_taint(TAINT_USER, LOCKDEP_STILL_OK);
> +
> +	return follow_pfn(vma, address, pfn);
> +#endif

Woudn't this be a pretty good use case of "if (IS_ENABLED(...)))"?

Also I'd expect the inverse polarity of the config option, that is
a USAFE_FOLLOW_PFN option to enable to unsafe behavior.

> +/**
> + * unsafe_follow_pfn - look up PFN at a user virtual address
> + * @vma: memory mapping
> + * @address: user virtual address
> + * @pfn: location to store found PFN
> + *
> + * Only IO mappings and raw PFN mappings are allowed.
> + *
> + * Returns zero and the pfn at @pfn on success, -ve otherwise.
> + */
> +int unsafe_follow_pfn(struct vm_area_struct *vma, unsigned long address,
> +	unsigned long *pfn)
> +{
> +	return follow_pfn(vma, address, pfn);
> +}
> +EXPORT_SYMBOL(unsafe_follow_pfn);

Any reason this doesn't use the warn and disable logic?

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  reply	other threads:[~2020-10-29  9:00 UTC|newest]

Thread overview: 88+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-26 10:58 [PATCH v4 00/15] follow_pfn and other iomap races Daniel Vetter
2020-10-26 10:58 ` Daniel Vetter
2020-10-26 10:58 ` Daniel Vetter
2020-10-26 10:58 ` [PATCH v4 01/15] drm/exynos: Stop using frame_vector helpers Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-26 10:58 ` [PATCH v4 02/15] drm/exynos: Use FOLL_LONGTERM for g2d cmdlists Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-26 10:58 ` [PATCH v4 03/15] misc/habana: Stop using frame_vector helpers Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-26 10:58 ` [PATCH v4 04/15] misc/habana: Use FOLL_LONGTERM for userptr Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-26 10:58 ` [PATCH v4 05/15] mm/frame-vector: Use FOLL_LONGTERM Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-26 22:15   ` Tomasz Figa
2020-10-26 22:15     ` Tomasz Figa
2020-10-26 22:15     ` Tomasz Figa
2020-10-26 22:15     ` Tomasz Figa
2020-10-27  8:05     ` Daniel Vetter
2020-10-27  8:05       ` Daniel Vetter
2020-10-27  8:05       ` Daniel Vetter
2020-10-26 10:58 ` [PATCH v4 06/15] media: videobuf2: Move frame_vector into media subsystem Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-26 22:03   ` Tomasz Figa
2020-10-26 22:03     ` Tomasz Figa
2020-10-26 22:03     ` Tomasz Figa
2020-10-26 22:03     ` Tomasz Figa
2020-10-26 10:58 ` [PATCH v4 07/15] mm: Close race in generic_access_phys Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-26 10:58 ` [PATCH v4 08/15] mm: Add unsafe_follow_pfn Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-29  8:56   ` Christoph Hellwig [this message]
2020-10-29  8:56     ` Christoph Hellwig
2020-10-29  9:23     ` Daniel Vetter
2020-10-29  9:23       ` Daniel Vetter
2020-10-29  9:23       ` Daniel Vetter
2020-10-29  9:23       ` Daniel Vetter
2020-10-29  9:23       ` Daniel Vetter
2020-10-26 10:58 ` [PATCH v4 09/15] media/videbuf1|2: Mark follow_pfn usage as unsafe Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-26 22:02   ` Tomasz Figa
2020-10-26 22:02     ` Tomasz Figa
2020-10-26 22:02     ` Tomasz Figa
2020-10-26 22:02     ` Tomasz Figa
2020-10-26 10:58 ` [PATCH v4 10/15] vfio/type1: Mark follow_pfn " Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-26 10:58 ` [PATCH v4 11/15] PCI: Obey iomem restrictions for procfs mmap Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-26 10:58 ` [PATCH v4 12/15] /dev/mem: Only set filp->f_mapping Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-26 10:58 ` [PATCH v4 13/15] resource: Move devmem revoke code to resource framework Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-26 10:58 ` [PATCH v4 14/15] sysfs: Support zapping of binary attr mmaps Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-26 10:58 ` [PATCH v4 15/15] PCI: Revoke mappings like devmem Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-26 10:58   ` Daniel Vetter
2020-10-29  8:57 ` [PATCH v4 00/15] follow_pfn and other iomap races Christoph Hellwig
2020-10-29  8:57   ` Christoph Hellwig
2020-10-29  9:25   ` Daniel Vetter
2020-10-29  9:25     ` Daniel Vetter
2020-10-29  9:25     ` Daniel Vetter
2020-10-29  9:25     ` Daniel Vetter
2020-10-29  9:25     ` Daniel Vetter
2020-10-29  9:28     ` Christoph Hellwig
2020-10-29  9:28       ` Christoph Hellwig
2020-10-29  9:28       ` Christoph Hellwig
2020-10-29  9:38       ` Daniel Vetter
2020-10-29  9:38         ` Daniel Vetter
2020-10-29  9:38         ` Daniel Vetter
2020-10-29  9:38         ` Daniel Vetter
2020-10-29  9:38         ` Daniel Vetter
2020-10-29 10:01         ` Christoph Hellwig
2020-10-29 10:01           ` Christoph Hellwig
2020-10-29 10:01           ` Christoph Hellwig

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