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Subject[patch] 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>
---
Index: linux-2.6/include/asm-x86/uaccess_64.h
===================================================================
--- linux-2.6.orig/include/asm-x86/uaccess_64.h
+++ linux-2.6/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);
Index: linux-2.6/include/asm-x86/uaccess.h
===================================================================
--- linux-2.6.orig/include/asm-x86/uaccess.h
+++ linux-2.6/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: \
Index: linux-2.6/arch/x86/lib/usercopy_32.c
===================================================================
--- linux-2.6.orig/arch/x86/lib/usercopy_32.c
+++ linux-2.6/arch/x86/lib/usercopy_32.c
@@ -33,6 +33,8 @@ static inline int __movsl_is_ok(unsigned
do { \
int __d0, __d1, __d2; \
might_sleep(); \
+ if (current->mm) \
+ might_lock_read(&current->mm->mmap_sem); \
__asm__ __volatile__( \
" testl %1,%1\n" \
" jz 2f\n" \
@@ -120,6 +122,8 @@ EXPORT_SYMBOL(strncpy_from_user);
do { \
int __d0; \
might_sleep(); \
+ if (current->mm) \
+ might_lock_read(&current->mm->mmap_sem); \
__asm__ __volatile__( \
"0: rep; stosl\n" \
" movl %2,%0\n" \
@@ -148,7 +152,6 @@ do { \
unsigned long
clear_user(void __user *to, unsigned long n)
{
- might_sleep();
if (access_ok(VERIFY_WRITE, to, n))
__do_clear_user(to, n);
return n;
@@ -191,6 +194,8 @@ long strnlen_user(const char __user *s,
unsigned long res, tmp;

might_sleep();
+ if (current->mm)
+ might_lock_read(&current->mm->mmap_sem);

__asm__ __volatile__(
" testl %0, %0\n"
Index: linux-2.6/arch/x86/lib/usercopy_64.c
===================================================================
--- linux-2.6.orig/arch/x86/lib/usercopy_64.c
+++ linux-2.6/arch/x86/lib/usercopy_64.c
@@ -16,6 +16,8 @@
do { \
long __d0, __d1, __d2; \
might_sleep(); \
+ if (current->mm) \
+ might_lock_read(&current->mm->mmap_sem); \
__asm__ __volatile__( \
" testq %1,%1\n" \
" jz 2f\n" \
@@ -65,6 +67,8 @@ unsigned long __clear_user(void __user *
{
long __d0;
might_sleep();
+ 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(
Index: linux-2.6/include/asm-x86/uaccess_32.h
===================================================================
--- linux-2.6.orig/include/asm-x86/uaccess_32.h
+++ linux-2.6/include/asm-x86/uaccess_32.h
@@ -82,8 +82,10 @@ __copy_to_user_inatomic(void __user *to,
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 __c
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;


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