From: Zong Li <zong.li@sifive.com>
To: akpm@linux-foundation.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, paul.walmsley@sifive.com,
palmer@dabbelt.com, linux-riscv@lists.infradead.org,
tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
x86@kernel.org, hpa@zytor.com, catalin.marinas@arm.com,
will@kernel.org, linux-arm-kernel@lists.infradead.org
Cc: Zong Li <zong.li@sifive.com>
Subject: [PATCH 1/4] mm: add DEBUG_WX support
Date: Tue, 21 Apr 2020 16:17:12 +0800 [thread overview]
Message-ID: <23980cd0f0e5d79e24a92169116407c75bcc650d.1587455584.git.zong.li@sifive.com> (raw)
In-Reply-To: <cover.1587455584.git.zong.li@sifive.com>
Some architectures support DEBUG_WX function, it's verbatim from each
others. Extract to mm/Kconfig.debug for shared use.
Signed-off-by: Zong Li <zong.li@sifive.com>
Suggested-by: Palmer Dabbelt <palmer@dabbelt.com>
---
mm/Kconfig.debug | 33 +++++++++++++++++++++++++++++++++
1 file changed, 33 insertions(+)
diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
index 0271b22e063f..077458ad968d 100644
--- a/mm/Kconfig.debug
+++ b/mm/Kconfig.debug
@@ -118,6 +118,39 @@ config DEBUG_RODATA_TEST
---help---
This option enables a testcase for the setting rodata read-only.
+config ARCH_HAS_DEBUG_WX
+ bool
+
+config DEBUG_WX
+ bool "Warn on W+X mappings at boot"
+ depends on ARCH_HAS_DEBUG_WX
+ select PTDUMP_CORE
+ help
+ Generate a warning if any W+X mappings are found at boot.
+
+ This is useful for discovering cases where the kernel is leaving
+ W+X mappings after applying NX, as such mappings are a security risk.
+ This check also includes UXN, which should be set on all kernel
+ mappings.
+
+ Look for a message in dmesg output like this:
+
+ <arch>/mm: Checked W+X mappings: passed, no W+X pages found.
+
+ or like this, if the check failed:
+
+ <arch>/mm: Checked W+X mappings: failed, <N> W+X pages found.
+
+ Note that even if the check fails, your kernel is possibly
+ still fine, as W+X mappings are not a security hole in
+ themselves, what they do is that they make the exploitation
+ of other unfixed kernel bugs easier.
+
+ There is no runtime or memory usage effect of this option
+ once the kernel has booted up - it's a one time check.
+
+ If in doubt, say "Y".
+
config GENERIC_PTDUMP
bool
--
2.26.1
next prev parent reply other threads:[~2020-04-21 8:17 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-21 8:17 [PATCH 0/4] Extract DEBUG_WX to shared use Zong Li
2020-04-21 8:17 ` Zong Li [this message]
2020-04-27 7:49 ` [PATCH 1/4] mm: add DEBUG_WX support Will Deacon
2020-04-27 8:47 ` Zong Li
2020-04-27 19:42 ` Andrew Morton
2020-04-21 8:17 ` [PATCH 2/4] riscv: support DEBUG_WX Zong Li
2020-04-26 1:05 ` Andrew Morton
2020-04-21 8:17 ` [PATCH 3/4] x86: mm: use ARCH_HAS_DEBUG_WX instead of arch defined Zong Li
2020-04-21 8:17 ` [PATCH 4/4] arm64: " Zong Li
2020-04-27 7:49 ` Will Deacon
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