linux-kernel - [PATCH -next] x86/efi_64: fix a user-memory-access in runtime

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Message-Id: <20200118063022.21743-1-cai@lca.pw>
Date:   Sat, 18 Jan 2020 01:30:22 -0500
From:   Qian Cai <cai@....pw>
To:     ardb@...nel.org
Cc:     mingo@...hat.com, kasan-dev@...glegroups.com,
        linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Qian Cai <cai@....pw>
Subject: [PATCH -next] x86/efi_64: fix a user-memory-access in runtime

The commit 698294704573 ("efi/x86: Split SetVirtualAddresMap() wrappers
into 32 and 64 bit versions") introduced a KASAN error during boot,

 BUG: KASAN: user-memory-access in efi_set_virtual_address_map+0x4d3/0x574
 Read of size 8 at addr 00000000788fee50 by task swapper/0/0

 Hardware name: HP ProLiant XL450 Gen9 Server/ProLiant XL450 Gen9
 Server, BIOS U21 05/05/2016
 Call Trace:
  dump_stack+0xa0/0xea
  __kasan_report.cold.8+0xb0/0xc0
  kasan_report+0x12/0x20
  __asan_load8+0x71/0xa0
  efi_set_virtual_address_map+0x4d3/0x574
  efi_enter_virtual_mode+0x5f3/0x64e
  start_kernel+0x53a/0x5dc
  x86_64_start_reservations+0x24/0x26
  x86_64_start_kernel+0xf4/0xfb
  secondary_startup_64+0xb6/0xc0

It points to this line,

status = efi_call(efi.systab->runtime->set_virtual_address_map,

efi.systab->runtime's address is 00000000788fee18 which is an address in
EFI runtime service and does not have a KASAN shadow page. Fix it by
doing a copy_from_user() first instead.

Fixes: 698294704573 ("efi/x86: Split SetVirtualAddresMap() wrappers into 32 and 64 bit versions")
Signed-off-by: Qian Cai <cai@....pw>
---
 arch/x86/platform/efi/efi_64.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index 515eab388b56..d6712c9cb9d8 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -1023,6 +1023,7 @@ efi_status_t __init efi_set_virtual_address_map(unsigned long memory_map_size,
 						u32 descriptor_version,
 						efi_memory_desc_t *virtual_map)
 {
+	efi_runtime_services_t runtime;
 	efi_status_t status;
 	unsigned long flags;
 	pgd_t *save_pgd = NULL;
@@ -1041,13 +1042,15 @@ efi_status_t __init efi_set_virtual_address_map(unsigned long memory_map_size,
 		efi_switch_mm(&efi_mm);
 	}
 
+	if (copy_from_user(&runtime, efi.systab->runtime, sizeof(runtime)))
+		return EFI_ABORTED;
+
 	kernel_fpu_begin();
 
 	/* Disable interrupts around EFI calls: */
 	local_irq_save(flags);
-	status = efi_call(efi.systab->runtime->set_virtual_address_map,
-			  memory_map_size, descriptor_size,
-			  descriptor_version, virtual_map);
+	status = efi_call(runtime.set_virtual_address_map, memory_map_size,
+			  descriptor_size, descriptor_version, virtual_map);
 	local_irq_restore(flags);
 
 	kernel_fpu_end();
-- 
2.21.0 (Apple Git-122.2)