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[68.4.215.93]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-21c2d3acf2csm62483555ad.121.2025.01.20.08.33.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 20 Jan 2025 08:33:09 -0800 (PST) Message-ID: <41550c7f-1313-41b4-aa2e-cb4809ad68c2@broadcom.com> Date: Mon, 20 Jan 2025 08:33:12 -0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] arm64: mm: account for hotplug memory when randomizing the linear region To: Greg KH 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 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> <2025012002-tactics-murky-aaab@gregkh> Content-Language: en-US From: Florian Fainelli Autocrypt: addr=florian.fainelli@broadcom.com; keydata= xsBNBFPAG8ABCAC3EO02urEwipgbUNJ1r6oI2Vr/+uE389lSEShN2PmL3MVnzhViSAtrYxeT M0Txqn1tOWoIc4QUl6Ggqf5KP6FoRkCrgMMTnUAINsINYXK+3OLe7HjP10h2jDRX4Ajs4Ghs JrZOBru6rH0YrgAhr6O5gG7NE1jhly+EsOa2MpwOiXO4DE/YKZGuVe6Bh87WqmILs9KvnNrQ PcycQnYKTVpqE95d4M824M5cuRB6D1GrYovCsjA9uxo22kPdOoQRAu5gBBn3AdtALFyQj9DQ KQuc39/i/Kt6XLZ/RsBc6qLs+p+JnEuPJngTSfWvzGjpx0nkwCMi4yBb+xk7Hki4kEslABEB AAHNMEZsb3JpYW4gRmFpbmVsbGkgPGZsb3JpYW4uZmFpbmVsbGlAYnJvYWRjb20uY29tPsLB IQQQAQgAywUCZWl41AUJI+Jo+hcKAAG/SMv+fS3xUQWa0NryPuoRGjsA3SAUAAAAAAAWAAFr ZXktdXNhZ2UtbWFza0BwZ3AuY29tjDAUgAAAAAAgAAdwcmVmZXJyZWQtZW1haWwtZW5jb2Rp bmdAcGdwLmNvbXBncG1pbWUICwkIBwMCAQoFF4AAAAAZGGxkYXA6Ly9rZXlzLmJyb2FkY29t Lm5ldAUbAwAAAAMWAgEFHgEAAAAEFQgJChYhBNXZKpfnkVze1+R8aIExtcQpvGagAAoJEIEx tcQpvGagWPEH/2l0DNr9QkTwJUxOoP9wgHfmVhqc0ZlDsBFv91I3BbhGKI5UATbipKNqG13Z TsBrJHcrnCqnTRS+8n9/myOF0ng2A4YT0EJnayzHugXm+hrkO5O9UEPJ8a+0553VqyoFhHqA zjxj8fUu1px5cbb4R9G4UAySqyeLLeqnYLCKb4+GklGSBGsLMYvLmIDNYlkhMdnnzsSUAS61 WJYW6jjnzMwuKJ0ZHv7xZvSHyhIsFRiYiEs44kiYjbUUMcXor/uLEuTIazGrE3MahuGdjpT2 IOjoMiTsbMc0yfhHp6G/2E769oDXMVxCCbMVpA+LUtVIQEA+8Zr6mX0Yk4nDS7OiBlvOwE0E U8AbwQEIAKxr71oqe+0+MYCc7WafWEcpQHFUwvYLcdBoOnmJPxDwDRpvU5LhqSPvk/yJdh9k 4xUDQu3rm1qIW2I9Puk5n/Jz/lZsqGw8T13DKyu8eMcvaA/irm9lX9El27DPHy/0qsxmxVmU pu9y9S+BmaMb2CM9IuyxMWEl9ruWFS2jAWh/R8CrdnL6+zLk60R7XGzmSJqF09vYNlJ6Bdbs MWDXkYWWP5Ub1ZJGNJQ4qT7g8IN0qXxzLQsmz6tbgLMEHYBGx80bBF8AkdThd6SLhreCN7Uh IR/5NXGqotAZao2xlDpJLuOMQtoH9WVNuuxQQZHVd8if+yp6yRJ5DAmIUt5CCPcAEQEAAcLB gQQYAQIBKwUCU8AbwgUbDAAAAMBdIAQZAQgABgUCU8AbwQAKCRCTYAaomC8PVQ0VCACWk3n+ obFABEp5Rg6Qvspi9kWXcwCcfZV41OIYWhXMoc57ssjCand5noZi8bKg0bxw4qsg+9cNgZ3P N/DFWcNKcAT3Z2/4fTnJqdJS//YcEhlr8uGs+ZWFcqAPbteFCM4dGDRruo69IrHfyyQGx16s CcFlrN8vD066RKevFepb/ml7eYEdN5SRALyEdQMKeCSf3mectdoECEqdF/MWpfWIYQ1hEfdm C2Kztm+h3Nkt9ZQLqc3wsPJZmbD9T0c9Rphfypgw/SfTf2/CHoYVkKqwUIzI59itl5Lze+R5 wDByhWHx2Ud2R7SudmT9XK1e0x7W7a5z11Q6vrzuED5nQvkhAAoJEIExtcQpvGagugcIAJd5 EYe6KM6Y6RvI6TvHp+QgbU5dxvjqSiSvam0Ms3QrLidCtantcGT2Wz/2PlbZqkoJxMQc40rb fXa4xQSvJYj0GWpadrDJUvUu3LEsunDCxdWrmbmwGRKqZraV2oG7YEddmDqOe0Xm/NxeSobc MIlnaE6V0U8f5zNHB7Y46yJjjYT/Ds1TJo3pvwevDWPvv6rdBeV07D9s43frUS6xYd1uFxHC 7dZYWJjZmyUf5evr1W1gCgwLXG0PEi9n3qmz1lelQ8lSocmvxBKtMbX/OKhAfuP/iIwnTsww 95A2SaPiQZA51NywV8OFgsN0ITl2PlZ4Tp9hHERDe6nQCsNI/Us= In-Reply-To: <2025012002-tactics-murky-aaab@gregkh> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 1/20/2025 5:59 AM, Greg KH wrote: > 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? We still have ARM64 systems running 5.4 that need this, and the same bug applies to 5.10 that we used to support but dropped in favor of 5.15/6.1. Those are the kernel versions used by Android, and Android TV in particular, so it's kind of the way it goes for us. > > Anyway, I need an ack from the ARM64 maintainers that this is ok to > apply here before I can take it. Just out of curiosity, the change is pretty innocuous and simple to review, why the extra scrutiny needed here? -- Florian