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From: David Hildenbrand <david@redhat.com>
To: David Laight <David.Laight@ACULAB.COM>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
	"stable@vger.kernel.org" <stable@vger.kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Axel Rasmussen <axelrasmussen@google.com>,
	Nadav Amit <nadav.amit@gmail.com>, Peter Xu <peterx@redhat.com>,
	Hugh Dickins <hughd@google.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Matthew Wilcox <willy@infradead.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	John Hubbard <jhubbard@nvidia.com>,
	Jason Gunthorpe <jgg@nvidia.com>
Subject: Re: [PATCH v2] mm/gup: fix FOLL_FORCE COW security issue and remove FOLL_COW
Date: Wed, 10 Aug 2022 11:18:16 +0200	[thread overview]
Message-ID: <b314c287-5fc2-9f61-53f6-33282a2bed92@redhat.com> (raw)
In-Reply-To: <afab7f23d10145b590aef44b3242db64@AcuMS.aculab.com>

On 10.08.22 11:12, David Laight wrote:
> From: David Hildenbrand
>> Sent: 09 August 2022 21:57
> ...
> 
> These two functions seem to contain a lot of the same tests.

Yes, but after Linus and I discussed to not even reuse is_cow_mapping()
but instead to spell it out, I refrained from factoring common checks
out here to harm readability.

[...]

> 
> Perhaps only the initial call (common success path?) should
> be inlined?
> With the flags and vma tests being moved to an inline helper.

Do we really care enough to hurt readability? I mean, most things here
are simple bit checks, not expensive function calls.

inline is only a hint to the compiler after all. Please correct me if
I'm wrong.


Now, I don't have any strong opinion, but I do want to make progress for
this because -stable trees still need fixing and I'll be posting the
reproducer on Monday.


Thanks

-- 
Thanks,

David / dhildenb


      reply	other threads:[~2022-08-10  9:18 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-08-09 20:56 [PATCH v2] mm/gup: fix FOLL_FORCE COW security issue and remove FOLL_COW David Hildenbrand
2022-08-10  9:12 ` David Laight
2022-08-10  9:18   ` David Hildenbrand [this message]

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