[PATCH] module/taint: Automatically increase the buffer size for new taint flags

[Petr Mladek]

The commit 66cc69e34e86a231 ("Fix: module signature vs tracepoints:
add new TAINT_UNSIGNED_MODULE") updated module_taint_flags() to
potentially print one more character. But it did not increase the
size of the corresponding buffers in m_show() and print_modules().

We have recently done the same mistake when adding a taint flag
for livepatching, see
https://lkml.kernel.org/g/cfba2c823bb984690b73572aaae1db596b54a082.1472137475.git.jpoimboe@xxxxxxxxxx

Let's convert the taint flags into enum and handle the buffer size
almost automatically.

It is not optimal because only few taint flags can be printed by
module_taint_flags(). But better be on the safe side. IMHO, it is
not worth the optimization and this is a good compromise.

Signed-off-by: Petr Mladek <pmladek@xxxxxxxx>
---
 include/linux/kernel.h | 44 ++++++++++++++++++++++++--------------------
 kernel/module.c        |  8 ++++++--
 kernel/panic.c         |  4 ++--
 3 files changed, 32 insertions(+), 24 deletions(-)

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index d96a6118d26a..1809bc82b7a5 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -472,14 +472,10 @@ static inline void set_arch_panic_timeout(int timeout, int arch_default_timeout)
 	if (panic_timeout == arch_default_timeout)
 		panic_timeout = timeout;
 }
-extern const char *print_tainted(void);
 enum lockdep_ok {
 	LOCKDEP_STILL_OK,
 	LOCKDEP_NOW_UNRELIABLE
 };
-extern void add_taint(unsigned flag, enum lockdep_ok);
-extern int test_taint(unsigned flag);
-extern unsigned long get_taint(void);
 extern int root_mountflags;
 
 extern bool early_boot_irqs_disabled;
@@ -493,22 +489,30 @@ extern enum system_states {
 	SYSTEM_RESTART,
 } system_state;
 
-#define TAINT_PROPRIETARY_MODULE	0
-#define TAINT_FORCED_MODULE		1
-#define TAINT_CPU_OUT_OF_SPEC		2
-#define TAINT_FORCED_RMMOD		3
-#define TAINT_MACHINE_CHECK		4
-#define TAINT_BAD_PAGE			5
-#define TAINT_USER			6
-#define TAINT_DIE			7
-#define TAINT_OVERRIDDEN_ACPI_TABLE	8
-#define TAINT_WARN			9
-#define TAINT_CRAP			10
-#define TAINT_FIRMWARE_WORKAROUND	11
-#define TAINT_OOT_MODULE		12
-#define TAINT_UNSIGNED_MODULE		13
-#define TAINT_SOFTLOCKUP		14
-#define TAINT_LIVEPATCH			15
+enum taint_flags {
+	TAINT_PROPRIETARY_MODULE,	/*  0 */
+	TAINT_FORCED_MODULE,		/*  1 */
+	TAINT_CPU_OUT_OF_SPEC,		/*  2 */
+	TAINT_FORCED_RMMOD,		/*  3 */
+	TAINT_MACHINE_CHECK,		/*  4 */
+	TAINT_BAD_PAGE,			/*  5 */
+	TAINT_USER,			/*  6 */
+	TAINT_DIE,			/*  7 */
+	TAINT_OVERRIDDEN_ACPI_TABLE,	/*  8 */
+	TAINT_WARN,			/*  9 */
+	TAINT_CRAP,			/* 10 */
+	TAINT_FIRMWARE_WORKAROUND,	/* 11 */
+	TAINT_OOT_MODULE,		/* 12 */
+	TAINT_UNSIGNED_MODULE,		/* 13 */
+	TAINT_SOFTLOCKUP,		/* 14 */
+	TAINT_LIVEPATCH,		/* 15 */
+	TAINT_FLAGS_COUNT		/* keep last! */
+};
+
+extern const char *print_tainted(void);
+extern void add_taint(enum taint_flags flag, enum lockdep_ok);
+extern int test_taint(enum taint_flags flag);
+extern unsigned long get_taint(void);
 
 extern const char hex_asc[];
 #define hex_asc_lo(x)	hex_asc[((x) & 0x0f)]
diff --git a/kernel/module.c b/kernel/module.c
index 529efae9f481..fb6c0d425b47 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -4036,6 +4036,10 @@ int module_kallsyms_on_each_symbol(int (*fn)(void *, const char *,
 }
 #endif /* CONFIG_KALLSYMS */
 
+/* Maximum number of characters written by module_flags() */
+#define MODULE_FLAGS_BUF_SIZE (TAINT_FLAGS_COUNT + 4)
+
+/* Keep in sync with MODULE_FLAGS_BUF_SIZE !!! */
 static char *module_flags(struct module *mod, char *buf)
 {
 	int bx = 0;
@@ -4080,7 +4084,7 @@ static void m_stop(struct seq_file *m, void *p)
 static int m_show(struct seq_file *m, void *p)
 {
 	struct module *mod = list_entry(p, struct module, list);
-	char buf[8];
+	char buf[MODULE_FLAGS_BUF_SIZE];
 
 	/* We always ignore unformed modules. */
 	if (mod->state == MODULE_STATE_UNFORMED)
@@ -4251,7 +4255,7 @@ EXPORT_SYMBOL_GPL(__module_text_address);
 void print_modules(void)
 {
 	struct module *mod;
-	char buf[8];
+	char buf[MODULE_FLAGS_BUF_SIZE];
 
 	printk(KERN_DEFAULT "Modules linked in:");
 	/* Most callers should already have preempt disabled, but make sure */
diff --git a/kernel/panic.c b/kernel/panic.c
index ca8cea1ef673..e90125bf9238 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -334,7 +334,7 @@ const char *print_tainted(void)
 	return buf;
 }
 
-int test_taint(unsigned flag)
+int test_taint(enum taint_flags flag)
 {
 	return test_bit(flag, &tainted_mask);
 }
@@ -353,7 +353,7 @@ unsigned long get_taint(void)
  * If something bad has gone wrong, you'll want @lockdebug_ok = false, but for
  * some notewortht-but-not-corrupting cases, it can be set to true.
  */
-void add_taint(unsigned flag, enum lockdep_ok lockdep_ok)
+void add_taint(enum taint_flags flag, enum lockdep_ok lockdep_ok)
 {
 	if (lockdep_ok == LOCKDEP_NOW_UNRELIABLE && __debug_locks_off())
 		pr_warn("Disabling lock debugging due to kernel taint\n");
-- 
1.8.5.6