From: Matthew Wilcox <willy@infradead.org>
To: Jan Stancek <jstancek@redhat.com>
Cc: linux-mm@kvack.org, akpm@linux-foundation.org,
peterz@infradead.org, riel@surriel.com, mhocko@suse.com,
ying.huang@intel.com, jrdr.linux@gmail.com, jglisse@redhat.com,
aneesh.kumar@linux.ibm.com, david@redhat.com,
aarcange@redhat.com, raquini@redhat.com, rientjes@google.com,
kirill@shutemov.name, mgorman@techsingularity.net,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/memory.c: do_fault: avoid usage of stale vm_area_struct
Date: Sat, 2 Mar 2019 09:10:43 -0800 [thread overview]
Message-ID: <20190302171043.GP11592@bombadil.infradead.org> (raw)
In-Reply-To: <0b7a4604529e16ace8d65a42dac7c78582e7fb28.1551538524.git.jstancek@redhat.com>
On Sat, Mar 02, 2019 at 04:11:26PM +0100, Jan Stancek wrote:
> Problem is that "vmf->vma" used in do_fault() can become stale.
> Because mmap_sem may be released, other threads can come in,
> call munmap() and cause "vma" be returned to kmem cache, and
> get zeroed/re-initialized and re-used:
> This patch pins mm_struct and stores its value, to avoid using
> potentially stale "vma" when calling pte_free().
OK, we need to cache the mm_struct, but why do we need the extra atomic op?
There's surely no way the mm can be freed while the thread is in the middle
of handling a fault.
ie I would drop these lines:
> + mmgrab(vm_mm);
> +
...
> +
> + mmdrop(vm_mm);
> +
next prev parent reply other threads:[~2019-03-02 17:10 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-02 15:11 [PATCH] mm/memory.c: do_fault: avoid usage of stale vm_area_struct Jan Stancek
2019-03-02 17:10 ` Matthew Wilcox [this message]
2019-03-02 18:00 ` Jan Stancek
2019-03-02 18:19 ` [PATCH v2] " Jan Stancek
2019-03-02 18:45 ` Peter Zijlstra
2019-03-02 18:51 ` Andrea Arcangeli
2019-03-03 7:27 ` Jan Stancek
2019-03-03 7:28 ` [PATCH v3] " Jan Stancek
2019-03-03 10:36 ` Matthew Wilcox
2019-03-04 0:13 ` Rafael Aquini
2019-03-04 8:10 ` Minchan Kim
2019-03-04 8:19 ` Kirill A. Shutemov
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