[v5,3/8] powerpc/mm/ptdump: debugfs handler for W+X checks at runtime
diff mbox series

Message ID 20200226063551.65363-4-ruscur@russell.cc
State New
Headers show
Series
  • set_memory() routines and STRICT_MODULE_RWX
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Commit Message

Russell Currey Feb. 26, 2020, 6:35 a.m. UTC
Very rudimentary, just

	echo 1 > [debugfs]/check_wx_pages

and check the kernel log.  Useful for testing strict module RWX.

Updated the Kconfig entry to reflect this.

Also fixed a typo.

Signed-off-by: Russell Currey <ruscur@russell.cc>
---
 arch/powerpc/Kconfig.debug      |  6 ++++--
 arch/powerpc/mm/ptdump/ptdump.c | 21 ++++++++++++++++++++-
 2 files changed, 24 insertions(+), 3 deletions(-)

Comments

Kees Cook Feb. 26, 2020, 9:52 p.m. UTC | #1
On Wed, Feb 26, 2020 at 05:35:46PM +1100, Russell Currey wrote:
> Very rudimentary, just
> 
> 	echo 1 > [debugfs]/check_wx_pages
> 
> and check the kernel log.  Useful for testing strict module RWX.
> 
> Updated the Kconfig entry to reflect this.

Oh, I like this! This would be handy to have on all architectures.

Reviewed-by: Kees Cook <keescook@chromium.org>

-Kees

> 
> Also fixed a typo.
> 
> Signed-off-by: Russell Currey <ruscur@russell.cc>
> ---
>  arch/powerpc/Kconfig.debug      |  6 ++++--
>  arch/powerpc/mm/ptdump/ptdump.c | 21 ++++++++++++++++++++-
>  2 files changed, 24 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug
> index 0b063830eea8..e37960ef68c6 100644
> --- a/arch/powerpc/Kconfig.debug
> +++ b/arch/powerpc/Kconfig.debug
> @@ -370,7 +370,7 @@ 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.
> @@ -384,7 +384,9 @@ 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 206156255247..a15e19a3b14e 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.
> @@ -413,6 +413,25 @@ 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)
> +		return -EINVAL;
> +
> +	ptdump_check_wx();
> +
> +	return 0;
> +}
> +
> +DEFINE_SIMPLE_ATTRIBUTE(check_wx_fops, NULL, 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
>

Patch
diff mbox series

diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug
index 0b063830eea8..e37960ef68c6 100644
--- a/arch/powerpc/Kconfig.debug
+++ b/arch/powerpc/Kconfig.debug
@@ -370,7 +370,7 @@  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.
@@ -384,7 +384,9 @@  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 206156255247..a15e19a3b14e 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.
@@ -413,6 +413,25 @@  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)
+		return -EINVAL;
+
+	ptdump_check_wx();
+
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(check_wx_fops, NULL, 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)