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From: Ard Biesheuvel <ardb@kernel.org>
To: linux-efi@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>
Cc: Ard Biesheuvel <ardb@kernel.org>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	linux-kernel@vger.kernel.org, Andy Lutomirski <luto@kernel.org>,
	Arvind Sankar <nivedita@alum.mit.edu>,
	Matthew Garrett <mjg59@google.com>
Subject: [PATCH 04/20] efi/x86: map the entire EFI vendor string before copying it
Date: Fri,  3 Jan 2020 12:39:37 +0100
Message-ID: <20200103113953.9571-5-ardb@kernel.org> (raw)
In-Reply-To: <20200103113953.9571-1-ardb@kernel.org>

Fix a couple of issues with the way we map and copy the vendor string:
- we map only 2 bytes, which usually works since you get at least a
  page, but if the vendor string happens to cross a page boundary,
  a crash will result
- only call early_memunmap() if early_memremap() succeeded, or we will
  call it with a NULL address which it doesn't like,
- while at it, switch to early_memremap_ro(), and array indexing rather
  than pointer dereferencing to read the CHAR16 characters.

Fixes: 5b83683f32b1 ("x86: EFI runtime service support")
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/x86/platform/efi/efi.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index d96953d9d4e7..3ce32c31bb61 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -541,7 +541,6 @@ void __init efi_init(void)
 	efi_char16_t *c16;
 	char vendor[100] = "unknown";
 	int i = 0;
-	void *tmp;
 
 #ifdef CONFIG_X86_32
 	if (boot_params.efi_info.efi_systab_hi ||
@@ -566,14 +565,16 @@ void __init efi_init(void)
 	/*
 	 * Show what we know for posterity
 	 */
-	c16 = tmp = early_memremap(efi.systab->fw_vendor, 2);
+	c16 = early_memremap_ro(efi.systab->fw_vendor,
+				sizeof(vendor) * sizeof(efi_char16_t));
 	if (c16) {
-		for (i = 0; i < sizeof(vendor) - 1 && *c16; ++i)
-			vendor[i] = *c16++;
+		for (i = 0; i < sizeof(vendor) - 1 && c16[i]; ++i)
+			vendor[i] = c16[i];
 		vendor[i] = '\0';
-	} else
+		early_memunmap(c16, sizeof(vendor) * sizeof(efi_char16_t));
+	} else {
 		pr_err("Could not map the firmware vendor!\n");
-	early_memunmap(tmp, 2);
+	}
 
 	pr_info("EFI v%u.%.02u by %s\n",
 		efi.systab->hdr.revision >> 16,
-- 
2.20.1


  parent reply index

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-03 11:39 [GIT PULL 00/20] More EFI updates for v5.6 Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 01/20] efi/libstub: fix boot argument handling in mixed mode entry code Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 02/20] efi/libstub/x86: force 'hidden' visibility for extern declarations Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 03/20] efi/x86: re-disable RT services for 32-bit kernels running on 64-bit EFI Ard Biesheuvel
2020-01-03 11:39 ` Ard Biesheuvel [this message]
2020-01-03 11:39 ` [PATCH 05/20] efi/x86: avoid redundant cast of EFI firmware service pointer Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 06/20] efi/x86: split off some old memmap handling into separate routines Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 07/20] efi/x86: split SetVirtualAddresMap() wrappers into 32 and 64 bit versions Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 08/20] efi/x86: simplify i386 efi_call_phys() firmware call wrapper Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 09/20] efi/x86: simplify 64-bit EFI " Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 10/20] efi/x86: simplify mixed mode " Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 11/20] efi/x86: drop two near identical versions of efi_runtime_init() Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 12/20] efi/x86: clean up efi_systab_init() routine for legibility Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 13/20] efi/x86: don't panic or BUG() on non-critical error conditions Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 14/20] efi/x86: remove unreachable code in kexec_enter_virtual_mode() Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 15/20] efi/x86: Check number of arguments to variadic functions Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 16/20] efi/x86: Allow translating 64-bit arguments for mixed mode calls Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 17/20] efi: Allow disabling PCI busmastering on bridges during boot Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 18/20] x86/mm: fix NX bit clearing issue in kernel_map_pages_in_pgd Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 19/20] efi/x86: don't map the entire kernel text RW for mixed mode Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 20/20] efi/x86: avoid RWX mappings for all of DRAM Ard Biesheuvel
2020-01-09  9:37 ` [GIT PULL 00/20] More EFI updates for v5.6 Ard Biesheuvel
2020-01-10 18:13   ` Ingo Molnar
2020-01-13  7:29     ` Ard Biesheuvel

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