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([2620:10d:c092:500::5:aa41]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a8d25d5491asm596445066b.198.2024.09.11.03.58.13 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 11 Sep 2024 03:58:14 -0700 (PDT) Message-ID: <8d3ec802-4f7e-42be-b757-bc103d039f0b@gmail.com> Date: Wed, 11 Sep 2024 11:58:13 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [edk2-devel] EFI table being corrupted during Kexec To: ardb@kernel.org, linux-efi@vger.kernel.org Cc: kexec@lists.infradead.org, bhe@redhat.com, vgoyal@redhat.com, devel@edk2.groups.io, rppt@kernel.org, gourry@gourry.net, rmikey@meta.com, afish@apple.com, kraxel@redhat.com, "Eric W. Biederman" , Breno Leitao References: <20240910-juicy-festive-sambar-9ad23a@devvm32600> <87ed5rd1qf.fsf@email.froward.int.ebiederm.org> From: Usama Arif In-Reply-To: <87ed5rd1qf.fsf@email.froward.int.ebiederm.org> Precedence: Bulk List-Subscribe: List-Help: Sender: devel@edk2.groups.io List-Id: Mailing-List: list devel@edk2.groups.io; contact devel+owner@edk2.groups.io Resent-Date: Wed, 11 Sep 2024 12:32:44 -0700 Resent-From: usamaarif642@gmail.com Reply-To: devel@edk2.groups.io,usamaarif642@gmail.com List-Unsubscribe-Post: List-Unsubscribe=One-Click List-Unsubscribe: Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-GND-Status: LEGIT Authentication-Results: spool.mail.gandi.net; dkim=pass header.d=groups.io header.s=20240830 header.b="GOcd+O/E"; dmarc=fail reason="SPF not aligned (relaxed), DKIM not aligned (relaxed)" header.from=gmail.com (policy=none); spf=pass (spool.mail.gandi.net: domain of bounce@groups.io designates 45.79.224.7 as permitted sender) smtp.mailfrom=bounce@groups.io On 10/09/2024 15:26, Eric W. Biederman wrote: > Breno Leitao writes: > >> We've seen a problem in upstream kernel kexec, where a EFI TPM log event table >> is being overwritten. This problem happen on real machine, as well as in a >> recent EDK2 qemu VM. >> >> Digging deep, the table is being overwritten during kexec, more precisely when >> relocating kernel (relocate_kernel() function). >> >> I've also found that the table is being properly reserved using >> memblock_reserve() early in the boot, and that range gets overwritten later in >> by relocate_kernel(). In other words, kexec is overwriting a memory that was >> previously reserved (as memblock_reserve()). >> >> Usama found that kexec only honours memory reservations from /sys/firmware/memmap >> which comes from e820_table_firmware table. >> >> Looking at the TPM spec, I found the following part: >> >> If the ACPI TPM2 table contains the address and size of the Platform Firmware TCG log, >> firmware “pins” the memory associated with the Platform Firmware TCG log, and reports >> this memory as “Reserved” memory via the INT 15h/E820 interface. >> >> >> From: https://trustedcomputinggroup.org/wp-content/uploads/PC-ClientPlatform_Profile_for_TPM_2p0_Systems_v49_161114_public-review.pdf >> >> I am wondering if that memory region/range should be part of e820 table that is >> passed by EFI firmware to kernel, and if it is not passed (as it is not being >> passed today), then the kernel doesn't need to respect it, and it is free to >> overwrite (as it does today). In other words, this is a firmware bug and not a >> kernel bug. >> >> Am I missing something? > > I agree that this appears to be a firmware bug. This memory is reserved > in one location and not in another location. > > That said that doesn't mean we can't deal with it in the kernel. > acpi_table_upgrade seems to have hit a similar issue issue and calls > arch_reserve_mem_area to reserve the area in the e820tables. > > > The last time I looked the e820 tables (in the kernel) are used to store > the efi memory map when available and only use the true e820 data on > older systems. > > Which is a long way of say that the e820 table in the kernel last I > looked was the master table, of how the firmware views the memory. > > > As I recall the memblock allocator is the bootstrap memory allocator > used when bringing up the kernel. So I don't see reserving something > in the memblock allocator as being authoritative as to how the firmware > has setup memory. > > > > I would suggest writing a patch to update whatever is calling > memblock_reserve to also, or perhaps in preference to update the e820 > map. If the code is not x86 specific I would suggest using ACPI's > arch_reserve_mem_area call. > Thanks, I have sent a potential fix for this at https://lore.kernel.org/all/20240911104109.1831501-1-usamaarif642@gmail.com/ We can see this issue in kernels going all the way back to 5.12. Up until now it only corrupted the tpm_log version, so it wasn't really an issue. After upgrading production to 6.9, the tpm_log size has started to get corrupted as well. When size was corrupted to a negative value, the memblock_reserve in efi_tpm_eventlog_init is reserving the entire memory available, and the system OOMs at boot time, which is causing a serious issue. It would be good to know if the above patch is an acceptable fix. Thanks! Usama -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#120552): https://edk2.groups.io/g/devel/message/120552 Mute This Topic: https://groups.io/mt/108376671/7686176 Group Owner: devel+owner@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [rebecca@openfw.io] -=-=-=-=-=-=-=-=-=-=-=-