From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B400A1E32BB; Mon, 20 Jan 2025 13:59:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737381587; cv=none; b=SF10fUd/r+/81w6nLfSvB5ETyDt5MndsSY1v4KBo9DpjeaKlAHC0xKt78b9FGTKltfJUUfmM2Uh93jmr84Tcp5K7/3SHNjDNi/gatEnFpBN/yBpE4ojS7lmO7QOSYQGwUkeyBiEiytJl2OUnfcfTAWWApvinZnFFX3QOiZgvY/c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737381587; c=relaxed/simple; bh=a6/AeNn2g3zqwiTDXTEbJ7QC16P6u39284X4lAoEtog=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=VyU5ohAW4buChMVKB+YUK5MxSfxD1YsKfiTK8XAyixoomTtdr8QZRiswSjaHRt2E+QHirM+YWMsHzmfPm6Da9DAywer8kP9k9WuiwaPvlNSPhvxnECVF0bRry0YhSf/giLFGdyh1ucA2yuHpAlA9JckVjALH7b37Tgt9UU2Vo8w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=2MLcyzMY; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="2MLcyzMY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A087EC4CEDD; Mon, 20 Jan 2025 13:59:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1737381587; bh=a6/AeNn2g3zqwiTDXTEbJ7QC16P6u39284X4lAoEtog=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=2MLcyzMYI9JONm6c1Gur2116gUNJAsgCEiKKY84RpZP6gkBZb11gm9p9UXYtX/s7c P9HCGU5kwWBjRYSrlmEIAQaMiccLo16sVEch//3ABkEC8U/Km4QE3aNgrTb1KVxLeJ xSfZLdVjtGpqPO+/0HhTEgNcSppIjvAsQ3LAPrxU= Date: Mon, 20 Jan 2025 14:59:44 +0100 From: Greg KH To: Florian Fainelli Cc: stable@vger.kernel.org, Ard Biesheuvel , Anshuman Khandual , Will Deacon , Steven Price , Robin Murphy , Catalin Marinas , Baruch Siach , Petr Tesarik , Mark Rutland , Joey Gouly , "Mike Rapoport (IBM)" , Yang Shi , "moderated list:ARM64 PORT (AARCH64 ARCHITECTURE)" , open list Subject: Re: [PATCH] arm64: mm: account for hotplug memory when randomizing the linear region Message-ID: <2025012002-tactics-murky-aaab@gregkh> References: <20250109165419.1623683-1-florian.fainelli@broadcom.com> <20250109165419.1623683-2-florian.fainelli@broadcom.com> <62786457-d4a1-4861-8bec-7e478626f4db@broadcom.com> <2025011247-enable-freezing-ffa2@gregkh> <27bbea11-61fa-4f41-8b39-8508f2d2e385@broadcom.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <27bbea11-61fa-4f41-8b39-8508f2d2e385@broadcom.com> On Mon, Jan 13, 2025 at 07:44:50AM -0800, Florian Fainelli wrote: > > > On 1/12/2025 3:54 AM, Greg KH wrote: > > On Thu, Jan 09, 2025 at 09:01:13AM -0800, Florian Fainelli wrote: > > > On 1/9/25 08:54, Florian Fainelli wrote: > > > > From: Ard Biesheuvel > > > > > > > > commit 97d6786e0669daa5c2f2d07a057f574e849dfd3e upstream > > > > > > > > As a hardening measure, we currently randomize the placement of > > > > physical memory inside the linear region when KASLR is in effect. > > > > Since the random offset at which to place the available physical > > > > memory inside the linear region is chosen early at boot, it is > > > > based on the memblock description of memory, which does not cover > > > > hotplug memory. The consequence of this is that the randomization > > > > offset may be chosen such that any hotplugged memory located above > > > > memblock_end_of_DRAM() that appears later is pushed off the end of > > > > the linear region, where it cannot be accessed. > > > > > > > > So let's limit this randomization of the linear region to ensure > > > > that this can no longer happen, by using the CPU's addressable PA > > > > range instead. As it is guaranteed that no hotpluggable memory will > > > > appear that falls outside of that range, we can safely put this PA > > > > range sized window anywhere in the linear region. > > > > > > > > Signed-off-by: Ard Biesheuvel > > > > Cc: Anshuman Khandual > > > > Cc: Will Deacon > > > > Cc: Steven Price > > > > Cc: Robin Murphy > > > > Link: https://lore.kernel.org/r/20201014081857.3288-1-ardb@kernel.org > > > > Signed-off-by: Catalin Marinas > > > > Signed-off-by: Florian Fainelli > > > > > > Forgot to update the patch subject, but this one is for 5.10. > > > > You also forgot to tell us _why_ this is needed :( > > This is explained in the second part of the first paragraph: > > The consequence of this is that the randomization offset may be chosen such > that any hotplugged memory located above memblock_end_of_DRAM() that appears > later is pushed off the end of the linear region, where it cannot be > accessed. > > We use both memory hotplug and KASLR on our systems and that's how we > eventually found out about the bug. And you still have 5.10.y ARM64 systems that need this? Why not move to a newer kernel version already? Anyway, I need an ack from the ARM64 maintainers that this is ok to apply here before I can take it. thanks, greg k-h