From: Jordan Niethe <jniethe5@gmail.com>
To: linuxppc-dev@lists.ozlabs.org
Cc: ajd@linux.ibm.com, Kees Cook <keescook@chromium.org>,
cmr@codefail.de, npiggin@gmail.com, naveen.n.rao@linux.ibm.com,
Jordan Niethe <jniethe5@gmail.com>,
dja@axtens.net
Subject: [PATCH v10 06/10] powerpc/mm/ptdump: debugfs handler for W+X checks at runtime
Date: Tue, 30 Mar 2021 15:51:28 +1100 [thread overview]
Message-ID: <20210330045132.722243-7-jniethe5@gmail.com> (raw)
In-Reply-To: <20210330045132.722243-1-jniethe5@gmail.com>
From: Russell Currey <ruscur@russell.cc>
Optionally run W+X checks when dumping pagetable information to
debugfs' kernel_page_tables.
To use:
$ echo 1 > /sys/kernel/debug/check_wx_pages
$ cat /sys/kernel/debug/kernel_page_tables
and check the kernel log. Useful for testing strict module RWX.
To disable W+X checks:
$ echo 0 > /sys/kernel/debug/check_wx_pages
Update the Kconfig entry to reflect this.
Also fix a typo.
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Russell Currey <ruscur@russell.cc>
[jpn: Change check_wx_pages to act as mode bit affecting
kernel_page_tables instead of triggering action on its own]
Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
---
v10: check_wx_pages now affects kernel_page_tables rather then triggers
its own action.
---
arch/powerpc/Kconfig.debug | 6 ++++--
arch/powerpc/mm/ptdump/ptdump.c | 34 ++++++++++++++++++++++++++++++++-
2 files changed, 37 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug
index ae084357994e..56e99e9a30d9 100644
--- a/arch/powerpc/Kconfig.debug
+++ b/arch/powerpc/Kconfig.debug
@@ -371,7 +371,7 @@ config PPC_PTDUMP
If you are unsure, say N.
config PPC_DEBUG_WX
- bool "Warn on W+X mappings at boot"
+ bool "Warn on W+X mappings at boot & enable manual checks at runtime"
depends on PPC_PTDUMP && STRICT_KERNEL_RWX
help
Generate a warning if any W+X mappings are found at boot.
@@ -385,7 +385,9 @@ config PPC_DEBUG_WX
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.
+ once the kernel has booted up, it only automatically checks once.
+
+ Enables the "check_wx_pages" debugfs entry for checking at runtime.
If in doubt, say "Y".
diff --git a/arch/powerpc/mm/ptdump/ptdump.c b/arch/powerpc/mm/ptdump/ptdump.c
index aca354fb670b..6592f7a48c96 100644
--- a/arch/powerpc/mm/ptdump/ptdump.c
+++ b/arch/powerpc/mm/ptdump/ptdump.c
@@ -4,7 +4,7 @@
*
* This traverses the kernel pagetables and dumps the
* information about the used sections of memory to
- * /sys/kernel/debug/kernel_pagetables.
+ * /sys/kernel/debug/kernel_page_tables.
*
* Derived from the arm64 implementation:
* Copyright (c) 2014, The Linux Foundation, Laura Abbott.
@@ -27,6 +27,8 @@
#include "ptdump.h"
+static bool check_wx;
+
/*
* To visualise what is happening,
*
@@ -410,6 +412,9 @@ static int ptdump_show(struct seq_file *m, void *v)
/* Traverse kernel page tables */
walk_pagetables(&st);
note_page(&st, 0, 0, 0, 0);
+
+ if (check_wx)
+ ptdump_check_wx();
return 0;
}
@@ -459,6 +464,33 @@ void ptdump_check_wx(void)
else
pr_info("Checked W+X mappings: passed, no W+X pages found\n");
}
+
+static int check_wx_debugfs_set(void *data, u64 val)
+{
+ if (val == 1ULL)
+ check_wx = true;
+ else if (val == 0ULL)
+ check_wx = false;
+ else
+ return -EINVAL;
+
+ return 0;
+}
+
+static int check_wx_debugfs_get(void *data, u64 *val)
+{
+ *val = check_wx ? 1 : 0;
+ return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(check_wx_fops, check_wx_debugfs_get, check_wx_debugfs_set, "%llu\n");
+
+static int ptdump_check_wx_init(void)
+{
+ return debugfs_create_file("check_wx_pages", 0200, NULL,
+ NULL, &check_wx_fops) ? 0 : -ENOMEM;
+}
+device_initcall(ptdump_check_wx_init);
#endif
static int ptdump_init(void)
--
2.25.1
next prev parent reply other threads:[~2021-03-30 4:54 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-30 4:51 [PATCH v10 00/10] powerpc: Further Strict RWX support Jordan Niethe
2021-03-30 4:51 ` [PATCH v10 01/10] powerpc/mm: Implement set_memory() routines Jordan Niethe
2021-03-30 5:16 ` Christophe Leroy
2021-04-21 2:51 ` Jordan Niethe
2021-03-31 11:16 ` Michael Ellerman
2021-03-31 12:03 ` Christophe Leroy
2021-04-21 5:03 ` Jordan Niethe
2021-04-01 4:37 ` Aneesh Kumar K.V
2021-04-21 5:19 ` Jordan Niethe
2021-03-30 4:51 ` [PATCH v10 02/10] powerpc/lib/code-patching: Set up Strict RWX patching earlier Jordan Niethe
2021-03-30 4:51 ` [PATCH v10 03/10] powerpc: Always define MODULES_{VADDR,END} Jordan Niethe
2021-03-30 5:00 ` Christophe Leroy
2021-04-01 13:36 ` Christophe Leroy
2021-04-21 2:46 ` Jordan Niethe
2021-04-21 5:14 ` Christophe Leroy
2021-04-21 5:22 ` Jordan Niethe
2021-03-30 4:51 ` [PATCH v10 04/10] powerpc/kprobes: Mark newly allocated probes as ROX Jordan Niethe
2021-03-30 5:05 ` Christophe Leroy
2021-04-21 2:39 ` Jordan Niethe
2021-03-30 4:51 ` [PATCH v10 05/10] powerpc/bpf: Write protect JIT code Jordan Niethe
2021-03-31 10:37 ` Michael Ellerman
2021-03-31 10:39 ` Christophe Leroy
2021-04-21 2:35 ` Jordan Niethe
2021-04-21 6:51 ` Michael Ellerman
2021-03-30 4:51 ` Jordan Niethe [this message]
2021-03-31 11:24 ` [PATCH v10 06/10] powerpc/mm/ptdump: debugfs handler for W+X checks at runtime Michael Ellerman
2021-04-21 2:23 ` Jordan Niethe
2021-04-21 5:16 ` Christophe Leroy
2021-03-30 4:51 ` [PATCH v10 07/10] powerpc: Set ARCH_HAS_STRICT_MODULE_RWX Jordan Niethe
2021-03-30 4:51 ` [PATCH v10 08/10] powerpc/configs: Enable STRICT_MODULE_RWX in skiroot_defconfig Jordan Niethe
2021-03-30 5:27 ` Christophe Leroy
2021-04-21 2:37 ` Jordan Niethe
2021-03-30 4:51 ` [PATCH v10 09/10] powerpc/mm: implement set_memory_attr() Jordan Niethe
2021-03-30 4:51 ` [PATCH v10 10/10] powerpc/32: use set_memory_attr() Jordan Niethe
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