From: Andrew Morton <akpm@linux-foundation.org>
To: "Thomas Hellström" <thomas_os@shipmail.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Thomas Hellstrom <thellstrom@vmware.com>,
Arnd Bergmann <arnd@arndb.de>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH 2/2] mm: Fix a huge pud insertion race during faulting
Date: Fri, 15 Nov 2019 11:58:00 -0800 [thread overview]
Message-ID: <20191115115800.45c053abcdb550d70b9baec9@linux-foundation.org> (raw)
In-Reply-To: <20191115115808.21181-2-thomas_os@shipmail.org>
On Fri, 15 Nov 2019 12:58:08 +0100 Thomas Hellström (VMware) <thomas_os@shipmail.org> wrote:
> A huge pud page can theoretically be faulted in racing with pmd_alloc()
> in __handle_mm_fault(). That will lead to pmd_alloc() returning an
> invalid pmd pointer. Fix this by adding a pud_trans_unstable() function
> similar to pmd_trans_unstable() and check whether the pud is really stable
> before using the pmd pointer.
>
> Race:
> Thread 1: Thread 2: Comment
> create_huge_pud() Fallback - not taken.
> create_huge_pud() Taken.
> pmd_alloc() Returns an invalid pointer.
What are the user-visible runtime effects of this change?
Is a -stable backport warranted?
next prev parent reply other threads:[~2019-11-15 19:58 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-15 11:58 [PATCH 1/2] mm: Move the backup x_devmap() functions to asm-generic/pgtable.h Thomas Hellström (VMware)
2019-11-15 11:58 ` [PATCH 2/2] mm: Fix a huge pud insertion race during faulting Thomas Hellström (VMware)
2019-11-15 19:58 ` Andrew Morton [this message]
2019-11-18 10:22 ` Kirill A. Shutemov
2019-11-18 12:58 ` Thomas Hellström (VMware)
2019-11-18 21:02 ` Andrew Morton
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