linux-hardening - [PATCH] lkdtm: Use init_uts

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Message-Id: <20210901233406.2571643-1-keescook@chromium.org>
Date:   Wed,  1 Sep 2021 16:34:06 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Kees Cook <keescook@...omium.org>, Arnd Bergmann <arnd@...db.de>,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: [PATCH] lkdtm: Use init_uts_ns.name instead of macros

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@...omium.org>
---
 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