linux-kernel - [PATCH 3.16 299/366] efi: Avoid potential crashes, fix the 'struct efi_pci_io_protocol

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Message-ID: <lsq.1539530741.263228050@decadent.org.uk>
Date:   Sun, 14 Oct 2018 16:25:41 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Hans de Goede" <hdegoede@...hat.com>,
        linux-efi@...r.kernel.org,
        "Matt Fleming" <matt@...eblueprint.co.uk>,
        "Ingo Molnar" <mingo@...nel.org>,
        "Linus Torvalds" <torvalds@...ux-foundation.org>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        "Peter Zijlstra" <peterz@...radead.org>,
        "Ard Biesheuvel" <ard.biesheuvel@...aro.org>
Subject: [PATCH 3.16 299/366] efi: Avoid potential crashes, fix the
 'struct efi_pci_io_protocol_32' definition for mixed mode

3.16.60-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Ard Biesheuvel <ard.biesheuvel@...aro.org>

commit 0b3225ab9407f557a8e20f23f37aa7236c10a9b1 upstream.

Mixed mode allows a kernel built for x86_64 to interact with 32-bit
EFI firmware, but requires us to define all struct definitions carefully
when it comes to pointer sizes.

'struct efi_pci_io_protocol_32' currently uses a 'void *' for the
'romimage' field, which will be interpreted as a 64-bit field
on such kernels, potentially resulting in bogus memory references
and subsequent crashes.

Tested-by: Hans de Goede <hdegoede@...hat.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Matt Fleming <matt@...eblueprint.co.uk>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-efi@...r.kernel.org
Link: http://lkml.kernel.org/r/20180504060003.19618-13-ard.biesheuvel@linaro.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/x86/boot/compressed/eboot.c | 6 ++++--
 include/linux/efi.h              | 8 ++++----
 2 files changed, 8 insertions(+), 6 deletions(-)

--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -358,7 +358,8 @@ __setup_efi_pci32(efi_pci_io_protocol_32
 	if (status != EFI_SUCCESS)
 		goto free_struct;
 
-	memcpy(rom->romdata, pci->romimage, pci->romsize);
+	memcpy(rom->romdata, (void *)(unsigned long)pci->romimage,
+	       pci->romsize);
 	return status;
 
 free_struct:
@@ -460,7 +461,8 @@ __setup_efi_pci64(efi_pci_io_protocol_64
 	if (status != EFI_SUCCESS)
 		goto free_struct;
 
-	memcpy(rom->romdata, pci->romimage, pci->romsize);
+	memcpy(rom->romdata, (void *)(unsigned long)pci->romimage,
+	       pci->romsize);
 	return status;
 
 free_struct:
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -368,8 +368,8 @@ typedef struct {
 	u32 attributes;
 	u32 get_bar_attributes;
 	u32 set_bar_attributes;
-	uint64_t romsize;
-	void *romimage;
+	u64 romsize;
+	u32 romimage;
 } efi_pci_io_protocol_32;
 
 typedef struct {
@@ -388,8 +388,8 @@ typedef struct {
 	u64 attributes;
 	u64 get_bar_attributes;
 	u64 set_bar_attributes;
-	uint64_t romsize;
-	void *romimage;
+	u64 romsize;
+	u64 romimage;
 } efi_pci_io_protocol_64;
 
 typedef struct {