Make the taint flags reliable

It's somewhat unlikely that it happens, but right now a race window
between interrupts or machine checks or oopses could corrupt the tainted
bitmap because it is modified in a non atomic fashion.

Convert the taint variable to an unsigned long and use only atomic bit
operations on it.

Unfortunately this means the intvec sysctl functions cannot be used on it
anymore.

It turned out the taint sysctl handler could actually be simplified a bit
(since it only increases capabilities) so this patch actually removes
code.

[[e-mail]: remove unneeded include]
Signed-off-by: Andi Kleen <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/x86/kernel/smpboot.c

···
 	cpu_set(cpuid, cpu_callin_map);
 }
 
+static int __cpuinitdata unsafe_smp;
+
 /*
  * Activate a secondary processor.
  */
···
 				goto valid_k7;
 
 		/* If we get here, not a certified SMP capable AMD system. */
-		add_taint(TAINT_UNSAFE_SMP);
+		unsafe_smp = 1;
 	}
 
 valid_k7:
···
 	 * Don't taint if we are running SMP kernel on a single non-MP
 	 * approved Athlon
 	 */
-	if (tainted & TAINT_UNSAFE_SMP) {
-		if (num_online_cpus())
-			printk(KERN_INFO "WARNING: This combination of AMD"
-				"processors is not suitable for SMP.\n");
-		else
-			tainted &= ~TAINT_UNSAFE_SMP;
+	if (unsafe_smp && num_online_cpus() > 1) {
+		printk(KERN_INFO "WARNING: This combination of AMD"
+			"processors is not suitable for SMP.\n");
+		add_taint(TAINT_UNSAFE_SMP);
 	}
 }
 

include/linux/kernel.h

···
 extern int panic_timeout;
 extern int panic_on_oops;
 extern int panic_on_unrecovered_nmi;
-extern int tainted;
 extern const char *print_tainted(void);
-extern void add_taint(unsigned);
+extern void add_taint(unsigned flag);
+extern int test_taint(unsigned flag);
+extern unsigned long get_taint(void);
 extern int root_mountflags;
 
 /* Values used for system_state */
···
 	SYSTEM_SUSPEND_DISK,
 } system_state;
 
-#define TAINT_PROPRIETARY_MODULE	(1<<0)
-#define TAINT_FORCED_MODULE		(1<<1)
-#define TAINT_UNSAFE_SMP		(1<<2)
-#define TAINT_FORCED_RMMOD		(1<<3)
-#define TAINT_MACHINE_CHECK		(1<<4)
-#define TAINT_BAD_PAGE			(1<<5)
-#define TAINT_USER			(1<<6)
-#define TAINT_DIE			(1<<7)
-#define TAINT_OVERRIDDEN_ACPI_TABLE	(1<<8)
-#define TAINT_WARN			(1<<9)
+#define TAINT_PROPRIETARY_MODULE	0
+#define TAINT_FORCED_MODULE		1
+#define TAINT_UNSAFE_SMP		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
 
 extern void dump_stack(void) __cold;
 

kernel/module.c

···
 static inline void add_taint_module(struct module *mod, unsigned flag)
 {
 	add_taint(flag);
-	mod->taints |= flag;
+	mod->taints |= (1U << flag);
 }
 
 /*
···
 static int try_to_force_load(struct module *mod, const char *symname)
 {
 #ifdef CONFIG_MODULE_FORCE_LOAD
-	if (!(tainted & TAINT_FORCED_MODULE))
+	if (!test_taint(TAINT_FORCED_MODULE))
 		printk("%s: no version for \"%s\" found: kernel tainted.\n",
 		       mod->name, symname);
 	add_taint_module(mod, TAINT_FORCED_MODULE);
···
 	const unsigned long *crc;
 
 	ret = find_symbol(name, &owner, &crc,
-			  !(mod->taints & TAINT_PROPRIETARY_MODULE), true);
+			  !(mod->taints & (1 << TAINT_PROPRIETARY_MODULE)), true);
 	if (!IS_ERR_VALUE(ret)) {
 		/* use_module can fail due to OOM,
 		   or module initialization or unloading */
···
 		license = "unspecified";
 
 	if (!license_is_gpl_compatible(license)) {
-		if (!(tainted & TAINT_PROPRIETARY_MODULE))
+		if (!test_taint(TAINT_PROPRIETARY_MODULE))
 			printk(KERN_WARNING "%s: module license '%s' taints "
 				"kernel.\n", mod->name, license);
 		add_taint_module(mod, TAINT_PROPRIETARY_MODULE);
···
 	    mod->state == MODULE_STATE_GOING ||
 	    mod->state == MODULE_STATE_COMING) {
 		buf[bx++] = '(';
-		if (mod->taints & TAINT_PROPRIETARY_MODULE)
+		if (mod->taints & (1 << TAINT_PROPRIETARY_MODULE))
 			buf[bx++] = 'P';
-		if (mod->taints & TAINT_FORCED_MODULE)
+		if (mod->taints & (1 << TAINT_FORCED_MODULE))
 			buf[bx++] = 'F';
 		/*
 		 * TAINT_FORCED_RMMOD: could be added.

kernel/panic.c

···
 #include <linux/kallsyms.h>
 
 int panic_on_oops;
-int tainted;
+static unsigned long tainted_mask;
 static int pause_on_oops;
 static int pause_on_oops_flag;
 static DEFINE_SPINLOCK(pause_on_oops_lock);
···
  *	The string is overwritten by the next call to print_taint().
  */
 
+struct tnt {
+	u8 bit;
+	char true;
+	char false;
+};
+
+static const struct tnt tnts[] = {
+	{ TAINT_PROPRIETARY_MODULE, 'P', 'G' },
+	{ TAINT_FORCED_MODULE, 'F', ' ' },
+	{ TAINT_UNSAFE_SMP, 'S', ' ' },
+	{ TAINT_FORCED_RMMOD, 'R', ' ' },
+	{ TAINT_MACHINE_CHECK, 'M', ' ' },
+	{ TAINT_BAD_PAGE, 'B', ' ' },
+	{ TAINT_USER, 'U', ' ' },
+	{ TAINT_DIE, 'D', ' ' },
+	{ TAINT_OVERRIDDEN_ACPI_TABLE, 'A', ' ' },
+	{ TAINT_WARN, 'W', ' ' },
+};
+
 const char *print_tainted(void)
 {
-	static char buf[20];
-	if (tainted) {
-		snprintf(buf, sizeof(buf), "Tainted: %c%c%c%c%c%c%c%c%c%c",
-			tainted & TAINT_PROPRIETARY_MODULE ? 'P' : 'G',
-			tainted & TAINT_FORCED_MODULE ? 'F' : ' ',
-			tainted & TAINT_UNSAFE_SMP ? 'S' : ' ',
-			tainted & TAINT_FORCED_RMMOD ? 'R' : ' ',
-			tainted & TAINT_MACHINE_CHECK ? 'M' : ' ',
-			tainted & TAINT_BAD_PAGE ? 'B' : ' ',
-			tainted & TAINT_USER ? 'U' : ' ',
-			tainted & TAINT_DIE ? 'D' : ' ',
-			tainted & TAINT_OVERRIDDEN_ACPI_TABLE ? 'A' : ' ',
-			tainted & TAINT_WARN ? 'W' : ' ');
-	}
-	else
+	static char buf[ARRAY_SIZE(tnts) + sizeof("Tainted: ") + 1];
+
+	if (tainted_mask) {
+		char *s;
+		int i;
+
+		s = buf + sprintf(buf, "Tainted: ");
+		for (i = 0; i < ARRAY_SIZE(tnts); i++) {
+			const struct tnt *t = &tnts[i];
+			*s++ = test_bit(t->bit, &tainted_mask) ?
+					t->true : t->false;
+		}
+		*s = 0;
+	} else
 		snprintf(buf, sizeof(buf), "Not tainted");
 	return(buf);
+}
+
+int test_taint(unsigned flag)
+{
+	return test_bit(flag, &tainted_mask);
+}
+EXPORT_SYMBOL(test_taint);
+
+unsigned long get_taint(void)
+{
+	return tainted_mask;
 }
 
 void add_taint(unsigned flag)
 {
 	debug_locks = 0; /* can't trust the integrity of the kernel anymore */
-	tainted |= flag;
+	set_bit(flag, &tainted_mask);
 }
 EXPORT_SYMBOL(add_taint);
 

kernel/softlockup.c

···
 	 * If the system crashed already then all bets are off,
 	 * do not report extra hung tasks:
 	 */
-	if ((tainted & TAINT_DIE) || did_panic)
+	if (test_taint(TAINT_DIE) || did_panic)
 		return;
 
 	read_lock(&tasklist_lock);

kernel/sysctl.c

···
 #ifdef CONFIG_PROC_SYSCTL
 static int proc_do_cad_pid(struct ctl_table *table, int write, struct file *filp,
 		  void __user *buffer, size_t *lenp, loff_t *ppos);
-static int proc_dointvec_taint(struct ctl_table *table, int write, struct file *filp,
+static int proc_taint(struct ctl_table *table, int write, struct file *filp,
 			       void __user *buffer, size_t *lenp, loff_t *ppos);
 #endif
 
···
 #ifdef CONFIG_PROC_SYSCTL
 	{
 		.procname	= "tainted",
-		.data		= &tainted,
-		.maxlen		= sizeof(int),
+		.maxlen 	= sizeof(long),
 		.mode		= 0644,
-		.proc_handler	= &proc_dointvec_taint,
+		.proc_handler	= &proc_taint,
 	},
 #endif
 #ifdef CONFIG_LATENCYTOP
···
 		    	    NULL,NULL);
 }
 
-#define OP_SET	0
-#define OP_AND	1
-#define OP_OR	2
-
-static int do_proc_dointvec_bset_conv(int *negp, unsigned long *lvalp,
-				      int *valp,
-				      int write, void *data)
-{
-	int op = *(int *)data;
-	if (write) {
-		int val = *negp ? -*lvalp : *lvalp;
-		switch(op) {
-		case OP_SET:	*valp = val; break;
-		case OP_AND:	*valp &= val; break;
-		case OP_OR:	*valp |= val; break;
-		}
-	} else {
-		int val = *valp;
-		if (val < 0) {
-			*negp = -1;
-			*lvalp = (unsigned long)-val;
-		} else {
-			*negp = 0;
-			*lvalp = (unsigned long)val;
-		}
-	}
-	return 0;
-}
-
 /*
- *	Taint values can only be increased
+ * Taint values can only be increased
+ * This means we can safely use a temporary.
  */
-static int proc_dointvec_taint(struct ctl_table *table, int write, struct file *filp,
+static int proc_taint(struct ctl_table *table, int write, struct file *filp,
 			       void __user *buffer, size_t *lenp, loff_t *ppos)
 {
-	int op;
+	struct ctl_table t;
+	unsigned long tmptaint = get_taint();
+	int err;
 
 	if (write && !capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
-	op = OP_OR;
-	return do_proc_dointvec(table,write,filp,buffer,lenp,ppos,
-				do_proc_dointvec_bset_conv,&op);
+	t = *table;
+	t.data = &tmptaint;
+	err = proc_doulongvec_minmax(&t, write, filp, buffer, lenp, ppos);
+	if (err < 0)
+		return err;
+
+	if (write) {
+		/*
+		 * Poor man's atomic or. Not worth adding a primitive
+		 * to everyone's atomic.h for this
+		 */
+		int i;
+		for (i = 0; i < BITS_PER_LONG && tmptaint >> i; i++) {
+			if ((tmptaint >> i) & 1)
+				add_taint(i);
+		}
+	}
+
+	return err;
 }
 
 struct do_proc_dointvec_minmax_conv_param {