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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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