From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Ingo Molnar <mingo@redhat.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andy Lutomirski <luto@amacapital.net>,
Nicholas Piggin <npiggin@gmail.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCHv2 1/2] x86/mm: Do not allow non-MAP_FIXED mapping across DEFAULT_MAP_WINDOW border
Date: Tue, 14 Nov 2017 22:21:13 +0300 [thread overview]
Message-ID: <20171114192113.t7pq5p2n5emmiw2n@node.shutemov.name> (raw)
In-Reply-To: <alpine.DEB.2.20.1711141630210.2044@nanos>
On Tue, Nov 14, 2017 at 05:01:50PM +0100, Thomas Gleixner wrote:
> On Tue, 14 Nov 2017, Kirill A. Shutemov wrote:
> > --- a/arch/x86/mm/hugetlbpage.c
> > +++ b/arch/x86/mm/hugetlbpage.c
> > @@ -166,11 +166,20 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
> >
> > if (addr) {
> > addr = ALIGN(addr, huge_page_size(h));
> > + if (TASK_SIZE - len >= addr)
> > + goto get_unmapped_area;
>
> That's wrong. You got it right in arch_get_unmapped_area_topdown() ...
Ouch.
Please ignore selftest patch. I'll rework it to cover hugetlb.
> > +
> > + /* See a comment in arch_get_unmapped_area_topdown */
>
> This is lame, really.
>
> > + if ((addr > DEFAULT_MAP_WINDOW) !=
> > + (addr + len > DEFAULT_MAP_WINDOW))
> > + goto get_unmapped_area;
>
> Instead of duplicating that horrible formatted condition and adding this
> lousy comment why can't you just put all of it (including the TASK_SIZE
> check) into a proper validation function and put the comment there?
>
> The fixed up variant of your patch below does that.
>
> Aside of that please spend a bit more time on describing things precisely
> at the technical and factual level next time. I fixed that up (once more)
> both in the comment and the changelog.
>
> Please double check.
Works fine.
> +bool mmap_address_hint_valid(unsigned long addr, unsigned long len)
> +{
> + if (TASK_SIZE - len < addr)
> + return false;
> +#if CONFIG_PGTABLE_LEVELS >= 5
> + return (addr > DEFAULT_MAP_WINDOW) == (addr + len > DEFAULT_MAP_WINDOW);
Is it micro optimization? I don't feel it necessary. It's not that hot
codepath to care about few cycles. (And one more place to care about for
boot-time switching.)
If you think it's needed, maybe IS_ENABLED() instead?
> +#else
> + return true;
> +#endif
> +}
--
Kirill A. Shutemov
--
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next prev parent reply other threads:[~2017-11-14 19:21 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-14 13:43 [PATCHv2 1/2] x86/mm: Do not allow non-MAP_FIXED mapping across DEFAULT_MAP_WINDOW border Kirill A. Shutemov
2017-11-14 13:43 ` [PATCHv2 2/2] x86/selftests: Add test for mapping placement for 5-level paging Kirill A. Shutemov
2017-11-14 16:01 ` [PATCHv2 1/2] x86/mm: Do not allow non-MAP_FIXED mapping across DEFAULT_MAP_WINDOW border Thomas Gleixner
2017-11-14 19:21 ` Kirill A. Shutemov [this message]
2017-11-14 20:29 ` Thomas Gleixner
2017-11-14 20:21 ` Kirill A. Shutemov
2017-11-14 20:54 ` Thomas Gleixner
2017-11-14 22:27 ` Kirill A. Shutemov
2017-11-14 23:00 ` Thomas Gleixner
2017-11-15 11:27 ` Kirill A. Shutemov
2017-11-15 11:39 ` Thomas Gleixner
2017-11-15 12:10 ` Kirill A. Shutemov
2017-11-15 14:04 ` Kirill A. Shutemov
2017-11-15 14:13 ` Kirill A. Shutemov
2017-11-15 14:23 ` Thomas Gleixner
2017-11-15 14:24 ` Kirill A. Shutemov
2017-11-15 14:18 ` Thomas Gleixner
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