x86: some lock annotations for user copy paths

copy_to/from_user and all its variants (except the atomic ones) can take a
page fault and perform non-trivial work like taking mmap_sem and entering
the filesyste/pagecache.

Unfortunately, this often escapes lockdep because a common pattern is to
use it to read in some arguments just set up from userspace, or write data
back to a hot buffer. In those cases, it will be unlikely for page reclaim
to get a window in to cause copy_*_user to fault.

With the new might_lock primitives, add some annotations to x86. I don't
know if I caught all possible faulting points (it's a bit of a maze, and I
didn't really look at 32-bit). But this is a starting point.

Boots and runs OK so far.

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>

3 files changed, 34 insertions, 2 deletions

diff --git a/include/asm-x86/uaccess.h b/include/asm-x86/uaccess.h
index 5f702d1d521..ad29752a171 100644
--- a/include/asm-x86/uaccess.h
+++ b/include/asm-x86/uaccess.h
@@ -8,6 +8,8 @@
 #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>
 
@@ -157,6 +159,9 @@ extern int __get_user_bad(void);
 	int __ret_gu;							\
 	unsigned long __val_gu;						\
 	__chk_user_ptr(ptr);						\
+	might_sleep();							\
+	if (current->mm)						\
+		might_lock_read(&current->mm->mmap_sem);		\
 	switch (sizeof(*(ptr))) {					\
 	case 1:								\
 		__get_user_x(1, __ret_gu, __val_gu, ptr);		\
@@ -241,6 +246,9 @@ extern void __put_user_8(void);
 	int __ret_pu;						\
 	__typeof__(*(ptr)) __pu_val;				\
 	__chk_user_ptr(ptr);					\
+	might_sleep();						\
+	if (current->mm)					\
+		might_lock_read(&current->mm->mmap_sem);	\
 	__pu_val = x;						\
 	switch (sizeof(*(ptr))) {				\
 	case 1:							\
@@ -265,6 +273,9 @@ extern void __put_user_8(void);
 #define __put_user_size(x, ptr, size, retval, errret)			\
 do {									\
 	retval = 0;							\
+	might_sleep();							\
+	if (current->mm)						\
+		might_lock_read(&current->mm->mmap_sem);		\
 	__chk_user_ptr(ptr);						\
 	switch (size) {							\
 	case 1:								\
@@ -317,6 +328,9 @@ do {									\
 #define __get_user_size(x, ptr, size, retval, errret)			\
 do {									\
 	retval = 0;							\
+	might_sleep();							\
+	if (current->mm)						\
+		might_lock_read(&current->mm->mmap_sem);		\
 	__chk_user_ptr(ptr);						\
 	switch (size) {							\
 	case 1:								\
diff --git a/include/asm-x86/uaccess_32.h b/include/asm-x86/uaccess_32.h
index 6fdef39a0bc..d725e2d703f 100644
--- a/include/asm-x86/uaccess_32.h
+++ b/include/asm-x86/uaccess_32.h
@@ -82,8 +82,10 @@ __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();
-       return __copy_to_user_inatomic(to, from, n);
+	might_sleep();
+	if (current->mm)
+		might_lock_read(&current->mm->mmap_sem);
+	return __copy_to_user_inatomic(to, from, n);
 }
 
 static __always_inline unsigned long
@@ -138,6 +140,8 @@ static __always_inline unsigned long
 __copy_from_user(void *to, const void __user *from, unsigned long n)
 {
 	might_sleep();
+	if (current->mm)
+		might_lock_read(&current->mm->mmap_sem);
 	if (__builtin_constant_p(n)) {
 		unsigned long ret;
 
@@ -160,6 +164,8 @@ static __always_inline unsigned long __copy_from_user_nocache(void *to,
 				const void __user *from, unsigned long n)
 {
 	might_sleep();
+	if (current->mm)
+		might_lock_read(&current->mm->mmap_sem);
 	if (__builtin_constant_p(n)) {
 		unsigned long ret;
 
diff --git a/include/asm-x86/uaccess_64.h b/include/asm-x86/uaccess_64.h
index 515d4dce96b..40a7205fe57 100644
--- a/include/asm-x86/uaccess_64.h
+++ b/include/asm-x86/uaccess_64.h
@@ -28,6 +28,10 @@ static __always_inline __must_check
 int __copy_from_user(void *dst, const void __user *src, unsigned size)
 {
 	int ret = 0;
+
+	might_sleep();
+	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) {
@@ -70,6 +74,10 @@ static __always_inline __must_check
 int __copy_to_user(void __user *dst, const void *src, unsigned size)
 {
 	int ret = 0;
+
+	might_sleep();
+	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) {
@@ -112,6 +120,10 @@ static __always_inline __must_check
 int __copy_in_user(void __user *dst, const void __user *src, unsigned size)
 {
 	int ret = 0;
+
+	might_sleep();
+	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);