Re: [PATCH] lkdtm: Use init_uts_ns.name instead of macros

From: Kees Cook
Date: Thu Sep 09 2021 - 11:50:02 EST


On Wed, Sep 01, 2021 at 04:34:06PM -0700, Kees Cook wrote:
> Using generated/compile.h triggered a full LKDTM rebuild with every
> build. Avoid this by using the exported strings instead.
>
> Fixes: b8661450bc7f ("lkdtm: Add kernel version to failure hints")
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>

Hi Greg,

Your bot said "please wait, the merge window is open", but it'd be really
nice to get this into -rc1 to avoid annoying people doing rebuilds...

:)

-Kees

> ---
> drivers/misc/lkdtm/core.c | 10 ++++++++++
> drivers/misc/lkdtm/lkdtm.h | 28 +++++++++++++++++-----------
> 2 files changed, 27 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c
> index 95b1c6800a22..fe6fd34b8caf 100644
> --- a/drivers/misc/lkdtm/core.c
> +++ b/drivers/misc/lkdtm/core.c
> @@ -26,6 +26,7 @@
> #include <linux/init.h>
> #include <linux/slab.h>
> #include <linux/debugfs.h>
> +#include <linux/utsname.h>
>
> #define DEFAULT_COUNT 10
>
> @@ -210,6 +211,8 @@ module_param(cpoint_count, int, 0644);
> MODULE_PARM_DESC(cpoint_count, " Crash Point Count, number of times the "\
> "crash point is to be hit to trigger action");
>
> +/* For test debug reporting. */
> +char *lkdtm_kernel_info;
>
> /* Return the crashtype number or NULL if the name is invalid */
> static const struct crashtype *find_crashtype(const char *name)
> @@ -490,6 +493,11 @@ static int __init lkdtm_module_init(void)
> crash_count = cpoint_count;
> #endif
>
> + /* Common initialization. */
> + lkdtm_kernel_info = kasprintf(GFP_KERNEL, "kernel (%s %s)",
> + init_uts_ns.name.release,
> + init_uts_ns.name.machine);
> +
> /* Handle test-specific initialization. */
> lkdtm_bugs_init(&recur_count);
> lkdtm_perms_init();
> @@ -538,6 +546,8 @@ static void __exit lkdtm_module_exit(void)
> if (lkdtm_kprobe != NULL)
> unregister_kprobe(lkdtm_kprobe);
>
> + kfree(lkdtm_kernel_info);
> +
> pr_info("Crash point unregistered\n");
> }
>
> diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h
> index d7d64d9765eb..c212a253edde 100644
> --- a/drivers/misc/lkdtm/lkdtm.h
> +++ b/drivers/misc/lkdtm/lkdtm.h
> @@ -5,17 +5,17 @@
> #define pr_fmt(fmt) "lkdtm: " fmt
>
> #include <linux/kernel.h>
> -#include <generated/compile.h>
> -#include <generated/utsrelease.h>
>
> -#define LKDTM_KERNEL "kernel (" UTS_RELEASE " " UTS_MACHINE ")"
> +extern char *lkdtm_kernel_info;
>
> #define pr_expected_config(kconfig) \
> { \
> if (IS_ENABLED(kconfig)) \
> - pr_err("Unexpected! This " LKDTM_KERNEL " was built with " #kconfig "=y\n"); \
> + pr_err("Unexpected! This %s was built with " #kconfig "=y\n", \
> + lkdtm_kernel_info); \
> else \
> - pr_warn("This is probably expected, since this " LKDTM_KERNEL " was built *without* " #kconfig "=y\n"); \
> + pr_warn("This is probably expected, since this %s was built *without* " #kconfig "=y\n", \
> + lkdtm_kernel_info); \
> }
>
> #ifndef MODULE
> @@ -25,24 +25,30 @@ int lkdtm_check_bool_cmdline(const char *param);
> if (IS_ENABLED(kconfig)) { \
> switch (lkdtm_check_bool_cmdline(param)) { \
> case 0: \
> - pr_warn("This is probably expected, since this " LKDTM_KERNEL " was built with " #kconfig "=y but booted with '" param "=N'\n"); \
> + pr_warn("This is probably expected, since this %s was built with " #kconfig "=y but booted with '" param "=N'\n", \
> + lkdtm_kernel_info); \
> break; \
> case 1: \
> - pr_err("Unexpected! This " LKDTM_KERNEL " was built with " #kconfig "=y and booted with '" param "=Y'\n"); \
> + pr_err("Unexpected! This %s was built with " #kconfig "=y and booted with '" param "=Y'\n", \
> + lkdtm_kernel_info); \
> break; \
> default: \
> - pr_err("Unexpected! This " LKDTM_KERNEL " was built with " #kconfig "=y (and booted without '" param "' specified)\n"); \
> + pr_err("Unexpected! This %s was built with " #kconfig "=y (and booted without '" param "' specified)\n", \
> + lkdtm_kernel_info); \
> } \
> } else { \
> switch (lkdtm_check_bool_cmdline(param)) { \
> case 0: \
> - pr_warn("This is probably expected, as this " LKDTM_KERNEL " was built *without* " #kconfig "=y and booted with '" param "=N'\n"); \
> + pr_warn("This is probably expected, as this %s was built *without* " #kconfig "=y and booted with '" param "=N'\n", \
> + lkdtm_kernel_info); \
> break; \
> case 1: \
> - pr_err("Unexpected! This " LKDTM_KERNEL " was built *without* " #kconfig "=y but booted with '" param "=Y'\n"); \
> + pr_err("Unexpected! This %s was built *without* " #kconfig "=y but booted with '" param "=Y'\n", \
> + lkdtm_kernel_info); \
> break; \
> default: \
> - pr_err("This is probably expected, since this " LKDTM_KERNEL " was built *without* " #kconfig "=y (and booted without '" param "' specified)\n"); \
> + pr_err("This is probably expected, since this %s was built *without* " #kconfig "=y (and booted without '" param "' specified)\n", \
> + lkdtm_kernel_info); \
> break; \
> } \
> } \
> --
> 2.30.2
>

--
Kees Cook