From: Catalin Marinas <catalin.marinas@arm.com>
To: Jianyong Wu <jianyong.wu@arm.com>
Cc: will@kernel.org, anshuman.khandual@arm.com,
akpm@linux-foundation.org, ardb@kernel.org,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, david@redhat.com,
gshan@redhat.com, justin.he@arm.com, nd@arm.com,
Mark Rutland <mark.rutland@arm.com>
Subject: Re: [PATCH v2] arm64/mm: avoid fixmap race condition when create pud mapping
Date: Fri, 10 Dec 2021 11:22:09 +0000 [thread overview]
Message-ID: <YbM4YTgXryp45ufk@arm.com> (raw)
In-Reply-To: <20211210095432.51798-1-jianyong.wu@arm.com>
On Fri, Dec 10, 2021 at 05:54:32PM +0800, Jianyong Wu wrote:
> fixmap is a global resource and is used recursively in create pud mapping.
> It may lead to race condition when alloc_init_pud is called concurrently.
>
> Fox example:
> alloc_init_pud is called when kernel_init. If memory hotplug
> thread, which will also call alloc_init_pud, happens during
> kernel_init, the race for fixmap occurs.
>
> The race condition flow can be:
>
> *************** begin **************
>
> kerenl_init thread virtio-mem workqueue thread
> ================== ======== ==================
> alloc_init_pud(...)
> pudp = pud_set_fixmap_offset(..) alloc_init_pud(...)
> ... ...
> READ_ONCE(*pudp) //OK! pudp = pud_set_fixmap_offset(
> ... ...
> pud_clear_fixmap() //fixmap break
> READ_ONCE(*pudp) //CRASH!
>
> **************** end ***************
>
> Hence, a spin lock is introduced to protect the fixmap during create pdg
> mapping.
>
> Signed-off-by: Jianyong Wu <jianyong.wu@arm.com>
It looks fine to me:
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Do we need a cc stable? Fixmap was introduced in 4.6, so usually:
Fixes: f4710445458c ("arm64: mm: use fixmap when creating page tables")
Cc: <stable@vger.kernel.org> # 4.6.x
but I haven't checked when memory hotplug was added to be able to
trigger the race. It may not need to go back that far.
--
Catalin
next prev parent reply other threads:[~2021-12-10 11:22 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-10 9:54 [PATCH v2] arm64/mm: avoid fixmap race condition when create pud mapping Jianyong Wu
2021-12-10 11:22 ` Catalin Marinas [this message]
2021-12-13 5:24 ` Jianyong Wu
2021-12-13 6:56 ` Anshuman Khandual
2021-12-13 7:27 ` Jianyong Wu
2021-12-13 7:37 ` David Hildenbrand
2021-12-13 9:57 ` Catalin Marinas
2021-12-13 10:16 ` Anshuman Khandual
2021-12-13 10:35 ` Ard Biesheuvel
2021-12-13 13:45 ` Will Deacon
2021-12-13 14:01 ` Ard Biesheuvel
2021-12-13 16:42 ` Will Deacon
2021-12-15 14:13 ` Qian Cai
2021-12-15 16:02 ` Catalin Marinas
2021-12-15 16:04 ` David Hildenbrand
2021-12-16 3:00 ` Jianyong Wu
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