linux-hardening - [PATCH v5 27/27] efi/x86: don't try to set page attributes on 0-sized regions.

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Date:   Tue, 14 Mar 2023 13:13:54 +0300
From:   Evgeniy Baskov <baskov@...ras.ru>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Peter Jones <pjones@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Alexey Khoroshilov <khoroshilov@...ras.ru>,
        Gerd Hoffmann <kraxel@...hat.com>,
        "Limonciello, Mario" <mario.limonciello@....com>,
        joeyli <jlee@...e.com>, lvc-project@...uxtesting.org,
        x86@...nel.org, linux-efi@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: [PATCH v5 27/27] efi/x86: don't try to set page attributes on 0-sized regions.

From: Peter Jones <pjones@...hat.com>

In "efi/x86: Explicitly set sections memory attributes", the following
region is defined to help compute page permissions:

          /* .setup [image_base, _head] */
          efi_adjust_memory_range_protection(image_base,
                                             (unsigned long)_head - image_base,
                                             EFI_MEMORY_RO | EFI_MEMORY_XP);

In at least some cases, that will result in a size of 0, which will
produce an error and a message on the console, though no actual failure
will be caused in the boot process.

This patch checks that case in efi_adjust_memory_range_protection() and
returns the error without logging.

Signed-off-by: Peter Jones <pjones@...hat.com>
---
 drivers/firmware/efi/libstub/mem.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/firmware/efi/libstub/mem.c b/drivers/firmware/efi/libstub/mem.c
index d58b552739ed..f18c797785ac 100644
--- a/drivers/firmware/efi/libstub/mem.c
+++ b/drivers/firmware/efi/libstub/mem.c
@@ -251,6 +251,9 @@ efi_status_t efi_adjust_memory_range_protection(unsigned long start,
 	efi_physical_addr_t rounded_start, rounded_end;
 	unsigned long attr_clear;
 
+	if (size == 0)
+		return EFI_INVALID_PARAMETER;
+
 	/*
 	 * This function should not be used to modify attributes
 	 * other than writable/executable.
-- 
2.39.2