x86: some lock annotations for user copy paths, v2

- introduce might_fault()
 - handle the atomic user copy paths correctly

[ mingo@elte.hu: move might_sleep() outside of in_atomic(). ]
Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/lib/usercopy_32.c

@@ -32,9 +32,7 @@ static inline int __movsl_is_ok(unsigned long a1, unsigned long a2, unsigned lon
 #define __do_strncpy_from_user(dst, src, count, res)			   \
 do {									   \
 	int __d0, __d1, __d2;						   \
-	might_sleep();							   \
+	might_fault();							   \
-	if (current->mm)						   \
-		might_lock_read(&current->mm->mmap_sem);		   \
 	__asm__ __volatile__(						   \
 		"	testl %1,%1\n"					   \
 		"	jz 2f\n"					   \
@@ -121,9 +119,7 @@ EXPORT_SYMBOL(strncpy_from_user);
 #define __do_clear_user(addr,size)					\
 do {									\
 	int __d0;							\
-	might_sleep();							\
+	might_fault();							\
-	if (current->mm)						\
-		might_lock_read(&current->mm->mmap_sem);		\
 	__asm__ __volatile__(						\
 		"0:	rep; stosl\n"					\
 		"	movl %2,%0\n"					\
@@ -193,9 +189,7 @@ long strnlen_user(const char __user *s, long n)
 	unsigned long mask = -__addr_ok(s);
 	unsigned long res, tmp;
 
-	might_sleep();
+	might_fault();
-	if (current->mm)
-		might_lock_read(&current->mm->mmap_sem);
 
 	__asm__ __volatile__(
 		"	testl %0, %0\n"

arch/x86/lib/usercopy_64.c

@@ -15,9 +15,7 @@
 #define __do_strncpy_from_user(dst,src,count,res)			   \
 do {									   \
 	long __d0, __d1, __d2;						   \
-	might_sleep();							   \
+	might_fault();							   \
-	if (current->mm)						   \
-		might_lock_read(&current->mm->mmap_sem);		   \
 	__asm__ __volatile__(						   \
 		"	testq %1,%1\n"					   \
 		"	jz 2f\n"					   \
@@ -66,9 +64,7 @@ EXPORT_SYMBOL(strncpy_from_user);
 unsigned long __clear_user(void __user *addr, unsigned long size)
 {
 	long __d0;
-	might_sleep();
+	might_fault();
-	if (current->mm)
-		might_lock_read(&current->mm->mmap_sem);
 	/* no memory constraint because it doesn't change any memory gcc knows
 	   about */
 	asm volatile(

include/asm-x86/uaccess.h

@@ -8,8 +8,6 @@
 #include <linux/thread_info.h>
 #include <linux/prefetch.h>
 #include <linux/string.h>
-#include <linux/lockdep.h>
-#include <linux/sched.h>
 #include <asm/asm.h>
 #include <asm/page.h>
 
@@ -159,9 +157,7 @@ extern int __get_user_bad(void);
 	int __ret_gu;							\
 	unsigned long __val_gu;						\
 	__chk_user_ptr(ptr);						\
-	might_sleep();							\
+	might_fault();							\
-	if (current->mm)						\
-		might_lock_read(&current->mm->mmap_sem);		\
 	switch (sizeof(*(ptr))) {					\
 	case 1:								\
 		__get_user_x(1, __ret_gu, __val_gu, ptr);		\
@@ -246,9 +242,7 @@ extern void __put_user_8(void);
 	int __ret_pu;						\
 	__typeof__(*(ptr)) __pu_val;				\
 	__chk_user_ptr(ptr);					\
-	might_sleep();						\
+	might_fault();						\
-	if (current->mm)					\
-		might_lock_read(&current->mm->mmap_sem);	\
 	__pu_val = x;						\
 	switch (sizeof(*(ptr))) {				\
 	case 1:							\
@@ -273,9 +267,7 @@ extern void __put_user_8(void);
 #define __put_user_size(x, ptr, size, retval, errret)			\
 do {									\
 	retval = 0;							\
-	might_sleep();							\
+	might_fault();							\
-	if (current->mm)						\
-		might_lock_read(&current->mm->mmap_sem);		\
 	__chk_user_ptr(ptr);						\
 	switch (size) {							\
 	case 1:								\
@@ -328,9 +320,7 @@ do {									\
 #define __get_user_size(x, ptr, size, retval, errret)			\
 do {									\
 	retval = 0;							\
-	might_sleep();							\
+	might_fault();							\
-	if (current->mm)						\
-		might_lock_read(&current->mm->mmap_sem);		\
 	__chk_user_ptr(ptr);						\
 	switch (size) {							\
 	case 1:								\

include/asm-x86/uaccess_32.h

@@ -82,9 +82,7 @@ __copy_to_user_inatomic(void __user *to, const void *from, unsigned long n)
 static __always_inline unsigned long __must_check
 __copy_to_user(void __user *to, const void *from, unsigned long n)
 {
-	might_sleep();
+	might_fault();
-	if (current->mm)
-		might_lock_read(&current->mm->mmap_sem);
 	return __copy_to_user_inatomic(to, from, n);
 }
 
@@ -139,9 +137,7 @@ __copy_from_user_inatomic(void *to, const void __user *from, unsigned long n)
 static __always_inline unsigned long
 __copy_from_user(void *to, const void __user *from, unsigned long n)
 {
-	might_sleep();
+	might_fault();
-	if (current->mm)
-		might_lock_read(&current->mm->mmap_sem);
 	if (__builtin_constant_p(n)) {
 		unsigned long ret;
 
@@ -163,9 +159,7 @@ __copy_from_user(void *to, const void __user *from, unsigned long n)
 static __always_inline unsigned long __copy_from_user_nocache(void *to,
 				const void __user *from, unsigned long n)
 {
-	might_sleep();
+	might_fault();
-	if (current->mm)
-		might_lock_read(&current->mm->mmap_sem);
 	if (__builtin_constant_p(n)) {
 		unsigned long ret;
 

include/asm-x86/uaccess_64.h

@@ -29,9 +29,7 @@ int __copy_from_user(void *dst, const void __user *src, unsigned size)
 {
 	int ret = 0;
 
-	might_sleep();
+	might_fault();
-	if (current->mm)
-		might_lock_read(&current->mm->mmap_sem);
 	if (!__builtin_constant_p(size))
 		return copy_user_generic(dst, (__force void *)src, size);
 	switch (size) {
@@ -75,9 +73,7 @@ int __copy_to_user(void __user *dst, const void *src, unsigned size)
 {
 	int ret = 0;
 
-	might_sleep();
+	might_fault();
-	if (current->mm)
-		might_lock_read(&current->mm->mmap_sem);
 	if (!__builtin_constant_p(size))
 		return copy_user_generic((__force void *)dst, src, size);
 	switch (size) {
@@ -121,9 +117,7 @@ int __copy_in_user(void __user *dst, const void __user *src, unsigned size)
 {
 	int ret = 0;
 
-	might_sleep();
+	might_fault();
-	if (current->mm)
-		might_lock_read(&current->mm->mmap_sem);
 	if (!__builtin_constant_p(size))
 		return copy_user_generic((__force void *)dst,
 					 (__force void *)src, size);

include/linux/kernel.h

@@ -140,6 +140,15 @@ extern int _cond_resched(void);
 		(__x < 0) ? -__x : __x;		\
 	})
 
+#ifdef CONFIG_PROVE_LOCKING
+void might_fault(void);
+#else
+static inline void might_fault(void)
+{
+	might_sleep();
+}
+#endif
+
 extern struct atomic_notifier_head panic_notifier_list;
 extern long (*panic_blink)(long time);
 NORET_TYPE void panic(const char * fmt, ...)

mm/memory.c

@@ -3016,3 +3016,18 @@ void print_vma_addr(char *prefix, unsigned long ip)
 	}
 	up_read(&current->mm->mmap_sem);
 }
+
+#ifdef CONFIG_PROVE_LOCKING
+void might_fault(void)
+{
+	might_sleep();
+	/*
+	 * it would be nicer only to annotate paths which are not under
+	 * pagefault_disable, however that requires a larger audit and
+	 * providing helpers like get_user_atomic.
+	 */
+	if (!in_atomic() && current->mm)
+		might_lock_read(&current->mm->mmap_sem);
+}
+EXPORT_SYMBOL(might_fault);
+#endif