linux-hardening - [PATCH 4/4] ptdump: add check_wx

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Date: Tue,  9 Jan 2024 13:14:38 +0100
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: linux-hardening@...r.kernel.org,
	Russell King <linux@...linux.org.uk>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@...nel.org>,
	"Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	Heiko Carstens <hca@...ux.ibm.com>,
	Vasily Gorbik <gor@...ux.ibm.com>,
	Alexander Gordeev <agordeev@...ux.ibm.com>,
	Christian Borntraeger <borntraeger@...ux.ibm.com>,
	Sven Schnelle <svens@...ux.ibm.com>,
	Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Andy Lutomirski <luto@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kees Cook <keescook@...omium.org>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org,
	linux-riscv@...ts.infradead.org,
	linux-s390@...r.kernel.org,
	linux-mm@...ck.org,
	steven.price@....com,
	Phong Tran <tranmanphong@...il.com>,
	mark.rutland@....com,
	Greg KH <greg@...ah.com>
Subject: [PATCH 4/4] ptdump: add check_wx_pages debugfs attribute

Add a writable attribute in debugfs to trigger a
W^X pages check at any time.

To trigger the test, just echo any numeric value into
/sys/kernel/debug/check_wx_pages

The result is provided into dmesg.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 mm/ptdump.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/mm/ptdump.c b/mm/ptdump.c
index 03c1bdae4a43..e154099c2584 100644
--- a/mm/ptdump.c
+++ b/mm/ptdump.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 
 #include <linux/pagewalk.h>
+#include <linux/debugfs.h>
 #include <linux/ptdump.h>
 #include <linux/kasan.h>
 
@@ -163,3 +164,21 @@ void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm, pgd_t *pgd)
 	/* Flush out the last page */
 	st->note_page(st, 0, -1, 0);
 }
+
+static int check_wx_debugfs_set(void *data, u64 val)
+{
+	ptdump_check_wx();
+
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(check_wx_fops, NULL, check_wx_debugfs_set, "%llu\n");
+
+static int ptdump_debugfs_init(void)
+{
+	debugfs_create_file("check_wx_pages", 0200, NULL, NULL, &check_wx_fops);
+
+	return 0;
+}
+
+device_initcall(ptdump_debugfs_init);
-- 
2.41.0