[PATCH v6 1/3] efi/x86: Fix EFI memory map corruption with kexec

[Ashish Kalra <Ashish.Kalra@amd.com>]

From: Ashish Kalra <ashish.kalra@amd.com>

With SNP guest kexec observe the following efi memmap corruption :

[    0.000000] efi: EFI v2.7 by EDK II
[    0.000000] efi: SMBIOS=0x7e33f000 SMBIOS 3.0=0x7e33d000 ACPI=0x7e57e000 ACPI 2.0=0x7e57e014 MEMATTR=0x7cc3c018 Unaccepted=0x7c09e018
[    0.000000] efi: [Firmware Bug]: Invalid EFI memory map entries:
[    0.000000] efi: mem03: [type=269370880|attr=0x0e42100e42180e41] range=[0x0486200e41038c18-0x200e898a0eee713ac17] (invalid)
[    0.000000] efi: mem04: [type=12336|attr=0x0e410686300e4105] range=[0x100e420000000176-0x8c290f26248d200e175] (invalid)
[    0.000000] efi: mem06: [type=1124304408|attr=0x000030b400000028] range=[0x0e51300e45280e77-0xb44ed2142f460c1e76] (invalid)
[    0.000000] efi: mem08: [type=68|attr=0x300e540583280e41] range=[0x0000011affff3cd8-0x486200e54b38c0bcd7] (invalid)
[    0.000000] efi: mem10: [type=1107529240|attr=0x0e42280e41300e41] range=[0x300e41058c280e42-0x38010ae54c5c328ee41] (invalid)
[    0.000000] efi: mem11: [type=189335566|attr=0x048d200e42038e18] range=[0x0000318c00000048-0xe42029228ce4200047] (invalid)
[    0.000000] efi: mem12: [type=239142534|attr=0x0000002400000b4b] range=[0x0e41380e0a7d700e-0x80f26238f22bfe500d] (invalid)
[    0.000000] efi: mem14: [type=239207055|attr=0x0e41300e43380e0a] range=[0x8c280e42048d200e-0xc70b028f2f27cc0a00d] (invalid)
[    0.000000] efi: mem15: [type=239210510|attr=0x00080e660b47080e] range=[0x0000324c0000001c-0xa78028634ce490001b] (invalid)
[    0.000000] efi: mem16: [type=4294848528|attr=0x0000329400000014] range=[0x0e410286100e4100-0x80f252036a218f20ff] (invalid)
[    0.000000] efi: mem19: [type=2250772033|attr=0x42180e42200e4328] range=[0x41280e0ab9020683-0xe0e538c28b39e62682] (invalid)
[    0.000000] efi: mem20: [type=16|   |  |  |  |  |  |  |  |  |   |WB|  |WC|  ] range=[0x00000008ffff4438-0xffff44340090333c437] (invalid)
[    0.000000] efi: mem22: [Reserved    |attr=0x000000c1ffff4420] range=[0xffff442400003398-0x1033a04240003f397] (invalid)
[    0.000000] efi: mem23: [type=1141080856|attr=0x080e41100e43180e] range=[0x280e66300e4b280e-0x440dc5ee7141f4c080d] (invalid)
[    0.000000] efi: mem25: [Reserved    |attr=0x0000000affff44a0] range=[0xffff44a400003428-0x1034304a400013427] (invalid)
[    0.000000] efi: mem28: [type=16|   |  |  |  |  |  |  |  |  |   |WB|  |WC|  ] range=[0x0000000affff4488-0xffff448400b034bc487] (invalid)
[    0.000000] efi: mem30: [Reserved    |attr=0x0000000affff4470] range=[0xffff447400003518-0x10352047400013517] (invalid)
[    0.000000] efi: mem33: [type=16|   |  |  |  |  |  |  |  |  |   |WB|  |WC|  ] range=[0x0000000affff4458-0xffff445400b035ac457] (invalid)
[    0.000000] efi: mem35: [type=269372416|attr=0x0e42100e42180e41] range=[0x0486200e44038c18-0x200e8b8a0eee823ac17] (invalid)
[    0.000000] efi: mem37: [type=2351435330|attr=0x0e42100e42180e42] range=[0x470783380e410686-0x2002b2a041c2141e685] (invalid)
[    0.000000] efi: mem38: [type=1093668417|attr=0x100e420000000270] range=[0x42100e42180e4220-0xfff366a4e421b78c21f] (invalid)
[    0.000000] efi: mem39: [type=76357646|attr=0x180e42200e42280e] range=[0x0e410686300e4105-0x4130f251a0710ae5104] (invalid)
[    0.000000] efi: mem40: [type=940444268|attr=0x0e42200e42280e41] range=[0x180e42200e42280e-0x300fc71c300b4f2480d] (invalid)
[    0.000000] efi: mem41: [MMIO        |attr=0x8c280e42048d200e] range=[0xffff479400003728-0x42138e0c87820292727] (invalid)
[    0.000000] efi: mem42: [type=1191674680|attr=0x0000004c0000000b] range=[0x300e41380e0a0246-0x470b0f26238f22b8245] (invalid)
[    0.000000] efi: mem43: [type=2010|attr=0x0301f00e4d078338] range=[0x45038e180e42028f-0xe4556bf118f282528e] (invalid)
[    0.000000] efi: mem44: [type=1109921345|attr=0x300e44000000006c] range=[0x44080e42100e4218-0xfff39254e42138ac217] (invalid)
...

This EFI memap corruption is happening with efi_arch_mem_reserve() invocation in case of kexec boot.

( efi_arch_mem_reserve() is invoked with the following call-stack: )

[    0.310010]  efi_arch_mem_reserve+0xb1/0x220
[    0.311382]  efi_mem_reserve+0x36/0x60
[    0.311973]  efi_bgrt_init+0x17d/0x1a0
[    0.313265]  acpi_parse_bgrt+0x12/0x20
[    0.313858]  acpi_table_parse+0x77/0xd0
[    0.314463]  acpi_boot_init+0x362/0x630
[    0.315069]  setup_arch+0xa88/0xf80
[    0.315629]  start_kernel+0x68/0xa90
[    0.316194]  x86_64_start_reservations+0x1c/0x30
[    0.316921]  x86_64_start_kernel+0xbf/0x110
[    0.317582]  common_startup_64+0x13e/0x141

efi_arch_mem_reserve() calls efi_memmap_alloc() to allocate memory for
EFI memory map and due to early allocation it uses memblock allocation.

Later during boot, efi_enter_virtual_mode() calls kexec_enter_virtual_mode()
in case of a kexec-ed kernel boot.

This function kexec_enter_virtual_mode() installs the new EFI memory map by
calling efi_memmap_init_late() which remaps the efi_memmap physically allocated
in efi_arch_mem_reserve(), but this remapping is still using memblock allocation.

Subsequently, when memblock is freed later in boot flow, this remapped
efi_memmap will have random corruption (similar to a use-after-free scenario).

The corrupted EFI memory map is then passed to the next kexec-ed kernel
which causes a panic when trying to use the corrupted EFI memory map.

Fix this EFI memory map corruption by skipping efi_arch_mem_reserve() for kexec.

Additionally, skipping this function for kexec altogther makes sense
as for kexec use case need to use the the EFI memmap passed from first
kernel via setup_data and avoid any additional EFI memory map
additions/updates.

Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
---
 arch/x86/platform/efi/quirks.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c
index f0cc00032751..af7126d9c540 100644
--- a/arch/x86/platform/efi/quirks.c
+++ b/arch/x86/platform/efi/quirks.c
@@ -258,6 +258,26 @@ void __init efi_arch_mem_reserve(phys_addr_t addr, u64 size)
 	int num_entries;
 	void *new;
 
+	/*
+	 * efi_arch_mem_reserve() calls efi_memmap_alloc() to allocate memory for
+	 * EFI memory map and due to early allocation it uses memblock allocation.
+	 * Later during boot, efi_enter_virtual_mode() calls kexec_enter_virtual_mode()
+	 * in case of a kexec-ed kernel boot. This function kexec_enter_virtual_mode()
+	 * installs the new EFI memory map by calling efi_memmap_init_late() which
+	 * remaps the efi_memmap physically allocated here in efi_arch_mem_reserve(),
+	 * but this remapping is still using memblock allocation.
+	 * Subsequently, when memblock is freed later in boot flow, this remapped
+	 * efi_memmap will have random corruption (similar to a use-after-free scenario).
+	 * The corrupted EFI memory map is then passed to the next kexec-ed kernel
+	 * which causes a panic when trying to use the corrupted EFI memory map.
+	 * Additionally, skipping this function for kexec altogther makes sense
+	 * as for kexec use case need to use the the EFI memmap passed from first
+	 * kernel via setup_data and avoid any additional EFI memory map
+	 * additions/updates.
+	 */
+	if (efi_setup)
+		return;
+
 	if (efi_mem_desc_lookup(addr, &md) ||
 	    md.type != EFI_BOOT_SERVICES_DATA) {
 		pr_err("Failed to lookup EFI memory descriptor for %pa\n", &addr);
-- 
2.34.1


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