From: Aditya Garg gargaditya08@live.com
On Apple T2 Macs, when Linux attempts to read the db and dbx efi variables at early boot to load UEFI Secure Boot certificates, a page fault occurs in Apple firmware code and EFI runtime services are disabled with the following logs:
[Firmware Bug]: Page fault caused by firmware at PA: 0xffffb1edc0068000 WARNING: CPU: 3 PID: 104 at arch/x86/platform/efi/quirks.c:735 efi_crash_gracefully_on_page_fault+0x50/0xf0 (Removed some logs from here) Call Trace: <TASK> page_fault_oops+0x4f/0x2c0 ? search_bpf_extables+0x6b/0x80 ? search_module_extables+0x50/0x80 ? search_exception_tables+0x5b/0x60 kernelmode_fixup_or_oops+0x9e/0x110 __bad_area_nosemaphore+0x155/0x190 bad_area_nosemaphore+0x16/0x20 do_kern_addr_fault+0x8c/0xa0 exc_page_fault+0xd8/0x180 asm_exc_page_fault+0x1e/0x30 (Removed some logs from here) ? __efi_call+0x28/0x30 ? switch_mm+0x20/0x30 ? efi_call_rts+0x19a/0x8e0 ? process_one_work+0x222/0x3f0 ? worker_thread+0x4a/0x3d0 ? kthread+0x17a/0x1a0 ? process_one_work+0x3f0/0x3f0 ? set_kthread_struct+0x40/0x40 ? ret_from_fork+0x22/0x30 </TASK> ---[ end trace 1f82023595a5927f ]--- efi: Froze efi_rts_wq and disabled EFI Runtime Services integrity: Couldn't get size: 0x8000000000000015 integrity: MODSIGN: Couldn't get UEFI db list efi: EFI Runtime Services are disabled! integrity: Couldn't get size: 0x8000000000000015 integrity: Couldn't get UEFI dbx list integrity: Couldn't get size: 0x8000000000000015 integrity: Couldn't get mokx list integrity: Couldn't get size: 0x80000000
So we avoid reading these UEFI variables and thus prevent the crash.
Cc: stable@vger.kernel.org Signed-off-by: Aditya Garg gargaditya08@live.com Reviewed-by: Mimi Zohar zohar@linux.ibm.com --- v2 :- Reduce code size of the table. v3 :- Close the brackets which were left open by mistake. v4 :- Fix comment style issues, remove blank spaces and limit use of dmi_first_match() v4 RESEND :- Add stable to cc v5 :- Rewrite the description v6 :- Make description more clear v7 :- Minor changes and add reviewed by .../platform_certs/keyring_handler.h | 8 +++++ security/integrity/platform_certs/load_uefi.c | 33 +++++++++++++++++++ 2 files changed, 41 insertions(+)
diff --git a/security/integrity/platform_certs/keyring_handler.h b/security/integrity/platform_certs/keyring_handler.h index 284558f30..212d894a8 100644 --- a/security/integrity/platform_certs/keyring_handler.h +++ b/security/integrity/platform_certs/keyring_handler.h @@ -35,3 +35,11 @@ efi_element_handler_t get_handler_for_mok(const efi_guid_t *sig_type); efi_element_handler_t get_handler_for_dbx(const efi_guid_t *sig_type);
#endif + +#ifndef UEFI_QUIRK_SKIP_CERT +#define UEFI_QUIRK_SKIP_CERT(vendor, product) \ + .matches = { \ + DMI_MATCH(DMI_BOARD_VENDOR, vendor), \ + DMI_MATCH(DMI_PRODUCT_NAME, product), \ + }, +#endif diff --git a/security/integrity/platform_certs/load_uefi.c b/security/integrity/platform_certs/load_uefi.c index 5f45c3c07..1a7e7d597 100644 --- a/security/integrity/platform_certs/load_uefi.c +++ b/security/integrity/platform_certs/load_uefi.c @@ -3,6 +3,7 @@ #include <linux/kernel.h> #include <linux/sched.h> #include <linux/cred.h> +#include <linux/dmi.h> #include <linux/err.h> #include <linux/efi.h> #include <linux/slab.h> @@ -12,6 +13,31 @@ #include "../integrity.h" #include "keyring_handler.h"
+/* + * On T2 Macs reading the db and dbx efi variables to load UEFI Secure Boot + * certificates causes occurrence of a page fault in Apple's firmware and + * a crash disabling EFI runtime services. The following quirk skips reading + * these variables. + */ +static const struct dmi_system_id uefi_skip_cert[] = { + { UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro15,1") }, + { UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro15,2") }, + { UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro15,3") }, + { UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro15,4") }, + { UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro16,1") }, + { UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro16,2") }, + { UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro16,3") }, + { UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro16,4") }, + { UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookAir8,1") }, + { UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookAir8,2") }, + { UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookAir9,1") }, + { UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacMini8,1") }, + { UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacPro7,1") }, + { UEFI_QUIRK_SKIP_CERT("Apple Inc.", "iMac20,1") }, + { UEFI_QUIRK_SKIP_CERT("Apple Inc.", "iMac20,2") }, + { } +}; + /* * Look to see if a UEFI variable called MokIgnoreDB exists and return true if * it does. @@ -138,6 +164,13 @@ static int __init load_uefi_certs(void) unsigned long dbsize = 0, dbxsize = 0, mokxsize = 0; efi_status_t status; int rc = 0; + const struct dmi_system_id *dmi_id; + + dmi_id = dmi_first_match(uefi_skip_cert); + if (dmi_id) { + pr_err("Reading UEFI Secure Boot Certs is not supported on T2 Macs.\n"); + return false; + }
if (!efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE)) return false;