From: Ard Biesheuvel <ardb@kernel.org>
To: linux-arm-kernel@lists.infradead.org
Cc: linux-acpi@vger.kernel.org, will@kernel.org,
catalin.marinas@arm.com, lorenzo.pieralisi@arm.com,
sudeep.holla@arm.com, kernel-hardening@lists.openwall.com,
Ard Biesheuvel <ardb@kernel.org>,
"Jason A . Donenfeld" <Jason@zx2c4.com>
Subject: [RFC PATCH] arm64/acpi: disallow AML memory opregions to access kernel memory
Date: Mon, 22 Jun 2020 11:27:19 +0200 [thread overview]
Message-ID: <20200622092719.1380968-1-ardb@kernel.org> (raw)
ACPI provides support for SystemMemory opregions, to allow AML methods
to access MMIO registers of, e.g., GPIO controllers, or access reserved
regions of memory that are owned by the firmware.
Currently, we also permit AML methods to access memory that is owned by
the kernel and mapped via the linear region, which does not seem to be
supported by a valid use case, and exposes the kernel's internal state
to AML methods that may be buggy and exploitable.
So close the door on this, and simply reject AML remapping requests for
any memory that has a valid mapping in the linear region.
Reported-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/arm64/include/asm/acpi.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
index a45366c3909b..18dcef4e6764 100644
--- a/arch/arm64/include/asm/acpi.h
+++ b/arch/arm64/include/asm/acpi.h
@@ -50,9 +50,9 @@ pgprot_t __acpi_get_mem_attribute(phys_addr_t addr);
static inline void __iomem *acpi_os_ioremap(acpi_physical_address phys,
acpi_size size)
{
- /* For normal memory we already have a cacheable mapping. */
+ /* Don't allow access to kernel memory from AML code */
if (memblock_is_map_memory(phys))
- return (void __iomem *)__phys_to_virt(phys);
+ return NULL;
/*
* We should still honor the memory's attribute here because
--
2.27.0
next reply other threads:[~2020-06-22 9:27 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-22 9:27 Ard Biesheuvel [this message]
2020-06-22 21:09 ` [RFC PATCH] arm64/acpi: disallow AML memory opregions to access kernel memory Jason A. Donenfeld
2020-06-22 21:15 ` Jason A. Donenfeld
2020-06-23 8:13 ` Will Deacon
2020-06-23 8:16 ` Ard Biesheuvel
2020-06-23 9:14 ` Will Deacon
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200622092719.1380968-1-ardb@kernel.org \
--to=ardb@kernel.org \
--cc=Jason@zx2c4.com \
--cc=catalin.marinas@arm.com \
--cc=kernel-hardening@lists.openwall.com \
--cc=linux-acpi@vger.kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=lorenzo.pieralisi@arm.com \
--cc=sudeep.holla@arm.com \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).