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authorZong Li <zong.li@sifive.com>2020-06-04 02:03:52 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2020-06-04 06:09:49 +0300
commit375d315cbfdb50e1eda099d4d004f7f401285111 (patch)
tree2d94b3c7be1f65cbf82c2cc10e92a4dd6b497ca2 /mm
parent4fb6eabf1037cfbef90a26412492aeae5580cf0a (diff)
downloadlinux-375d315cbfdb50e1eda099d4d004f7f401285111.tar.xz
mm: add DEBUG_WX support
Patch series "Extract DEBUG_WX to shared use". Some architectures support DEBUG_WX function, it's verbatim from each others, so extract to mm/Kconfig.debug for shared use. PPC and ARM ports don't support generic page dumper yet, so we only refine x86 and arm64 port in this patch series. For RISC-V port, the DEBUG_WX support depends on other patches which be merged already: - RISC-V page table dumper - Support strict kernel memory permissions for security This patch (of 4): Some architectures support DEBUG_WX function, it's verbatim from each others. Extract to mm/Kconfig.debug for shared use. [akpm@linux-foundation.org: reword text, per Will Deacon & Zong Li] Link: http://lkml.kernel.org/r/20200427194245.oxRJKj3fn%25akpm@linux-foundation.org [zong.li@sifive.com: remove the specific name of arm64] Link: http://lkml.kernel.org/r/3a6a92ecedc54e1d0fc941398e63d504c2cd5611.1589178399.git.zong.li@sifive.com [zong.li@sifive.com: add MMU dependency for DEBUG_WX] Link: http://lkml.kernel.org/r/4a674ac7863ff39ca91847b10e51209771f99416.1589178399.git.zong.li@sifive.com Suggested-by: Palmer Dabbelt <palmer@dabbelt.com> Signed-off-by: Zong Li <zong.li@sifive.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Paul Walmsley <paul.walmsley@sifive.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org> Link: http://lkml.kernel.org/r/cover.1587455584.git.zong.li@sifive.com Link: http://lkml.kernel.org/r/23980cd0f0e5d79e24a92169116407c75bcc650d.1587455584.git.zong.li@sifive.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/Kconfig.debug32
1 files changed, 32 insertions, 0 deletions
diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
index 0271b22e063f..2409f7fc1567 100644
--- a/mm/Kconfig.debug
+++ b/mm/Kconfig.debug
@@ -118,6 +118,38 @@ 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
+ depends on MMU
+ 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.
+
+ 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