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Date: Tue, 6 Nov 2018 12:56:52 -0500
From: Sasha Levin <sashal@kernel.org>
To: Paul Burton <paul.burton@mips.com>
Cc: "stable@vger.kernel.org" <stable@vger.kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Huacai Chen <chenhc@lemote.com>,
        Paul Burton <pburton@wavecomp.com>,
        Ralf Baechle <ralf@linux-mips.org>,
        James Hogan <jhogan@kernel.org>,
        "linux-mips@linux-mips.org" <linux-mips@linux-mips.org>,
        Fuxin Zhang <zhangfx@lemote.com>,
        Zhangjin Wu <wuzhangjin@gmail.com>,
        Huacai Chen <chenhuacai@gmail.com>
Subject: Re: [4.19 PATCH] MIPS: VDSO: Reduce VDSO_RANDOMIZE_SIZE to 64MB for
 64bit
Message-ID: <20181106175652.GF151445@sasha-vm>
References: <20181105225815.24489-1-paul.burton@mips.com>
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On Mon, Nov 05, 2018 at 10:58:30PM +0000, Paul Burton wrote:
>From: Huacai Chen <chenhc@lemote.com>
>
>[ Upstream commit c61c7def1fa0a722610d89790e0255b74f3c07dd ]
>
>Commit ea7e0480a4b6 ("MIPS: VDSO: Always map near top of user memory")
>set VDSO_RANDOMIZE_SIZE to 256MB for 64bit kernel. But take a look at
>arch/mips/mm/mmap.c we can see that MIN_GAP is 128MB, which means the
>mmap_base may be at (user_address_top - 128MB). This make the stack be
>surrounded by mmaped areas, then stack expanding fails and causes a
>segmentation fault. Therefore, VDSO_RANDOMIZE_SIZE should be less than
>MIN_GAP and this patch reduce it to 64MB.
>
>Signed-off-by: Huacai Chen <chenhc@lemote.com>
>Signed-off-by: Paul Burton <paul.burton@mips.com>
>Fixes: ea7e0480a4b6 ("MIPS: VDSO: Always map near top of user memory")
>Patchwork: https://patchwork.linux-mips.org/patch/20910/
>Cc: Ralf Baechle <ralf@linux-mips.org>
>Cc: James Hogan <jhogan@kernel.org>
>Cc: linux-mips@linux-mips.org
>Cc: Fuxin Zhang <zhangfx@lemote.com>
>Cc: Zhangjin Wu <wuzhangjin@gmail.com>
>Cc: Huacai Chen <chenhuacai@gmail.com>
>Cc: stable@vger.kernel.org # 4.19

Now queued for 4.19, thank you.

--
Thanks,
Sasha