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linux/arch/x86/include/asm/uaccess.h
Linus Torvalds 9063c61fd5 x86, 64-bit: Clean up user address masking 
The discussion about using "access_ok()" in get_user_pages_fast() (see
commit 7f81890687: "x86: don't use
'access_ok()' as a range check in get_user_pages_fast()" for details and
end result), made us notice that x86-64 was really being very sloppy
about virtual address checking.

So be way more careful and straightforward about masking x86-64 virtual
addresses:

 - All the VIRTUAL_MASK* variants now cover half of the address
   space, it's not like we can use the full mask on a signed
   integer, and the larger mask just invites mistakes when
   applying it to either half of the 48-bit address space.

 - /proc/kcore's kc_offset_to_vaddr() becomes a lot more
   obvious when it transforms a file offset into a
   (kernel-half) virtual address.

 - Unify/simplify the 32-bit and 64-bit USER_DS definition to
   be based on TASK_SIZE_MAX.

This cleanup and more careful/obvious user virtual address checking also
uncovered a buglet in the x86-64 implementation of strnlen_user(): it
would do an "access_ok()" check on the whole potential area, even if the
string itself was much shorter, and thus return an error even for valid
strings. Our sloppy checking had hidden this.

So this fixes 'strnlen_user()' to do this properly, the same way we
already handled user strings in 'strncpy_from_user()'.  Namely by just
checking the first byte, and then relying on fault handling for the
rest.  That always works, since we impose a guard page that cannot be
mapped at the end of the user space address space (and even if we
didn't, we'd have the address space hole).

Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-06-20 15:40:00 -07:00

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#ifndef _ASM_X86_UACCESS_H
#define _ASM_X86_UACCESS_H
/*
* User space memory access functions
*/
#include <linux/errno.h>
#include <linux/compiler.h>
#include <linux/thread_info.h>
#include <linux/prefetch.h>
#include <linux/string.h>
#include <asm/asm.h>
#include <asm/page.h>
#define VERIFY_READ 0
#define VERIFY_WRITE 1
/*
* The fs value determines whether argument validity checking should be
* performed or not. If get_fs() == USER_DS, checking is performed, with
* get_fs() == KERNEL_DS, checking is bypassed.
*
* For historical reasons, these macros are grossly misnamed.
*/
#define MAKE_MM_SEG(s) ((mm_segment_t) { (s) })
#define KERNEL_DS MAKE_MM_SEG(-1UL)
#define USER_DS MAKE_MM_SEG(TASK_SIZE_MAX)
#define get_ds() (KERNEL_DS)
#define get_fs() (current_thread_info()->addr_limit)
#define set_fs(x) (current_thread_info()->addr_limit = (x))
#define segment_eq(a, b) ((a).seg == (b).seg)
#define __addr_ok(addr) \
((unsigned long __force)(addr) < \
(current_thread_info()->addr_limit.seg))
/*
* Test whether a block of memory is a valid user space address.
* Returns 0 if the range is valid, nonzero otherwise.
*
* This is equivalent to the following test:
* (u33)addr + (u33)size >= (u33)current->addr_limit.seg (u65 for x86_64)
*
* This needs 33-bit (65-bit for x86_64) arithmetic. We have a carry...
*/
#define __range_not_ok(addr, size) \
({ \
unsigned long flag, roksum; \
__chk_user_ptr(addr); \
asm("add %3,%1 ; sbb %0,%0 ; cmp %1,%4 ; sbb $0,%0" \
: "=&r" (flag), "=r" (roksum) \
: "1" (addr), "g" ((long)(size)), \
"rm" (current_thread_info()->addr_limit.seg)); \
flag; \
})
/**
* access_ok: - Checks if a user space pointer is valid
* @type: Type of access: %VERIFY_READ or %VERIFY_WRITE. Note that
* %VERIFY_WRITE is a superset of %VERIFY_READ - if it is safe
* to write to a block, it is always safe to read from it.
* @addr: User space pointer to start of block to check
* @size: Size of block to check
*
* Context: User context only. This function may sleep.
*
* Checks if a pointer to a block of memory in user space is valid.
*
* Returns true (nonzero) if the memory block may be valid, false (zero)
* if it is definitely invalid.
*
* Note that, depending on architecture, this function probably just
* checks that the pointer is in the user space range - after calling
* this function, memory access functions may still return -EFAULT.
*/
#define access_ok(type, addr, size) (likely(__range_not_ok(addr, size) == 0))
/*
* The exception table consists of pairs of addresses: the first is the
* address of an instruction that is allowed to fault, and the second is
* the address at which the program should continue. No registers are
* modified, so it is entirely up to the continuation code to figure out
* what to do.
*
* All the routines below use bits of fixup code that are out of line
* with the main instruction path. This means when everything is well,
* we don't even have to jump over them. Further, they do not intrude
* on our cache or tlb entries.
*/
struct exception_table_entry {
unsigned long insn, fixup;
};
extern int fixup_exception(struct pt_regs *regs);
/*
* These are the main single-value transfer routines. They automatically
* use the right size if we just have the right pointer type.
*
* This gets kind of ugly. We want to return _two_ values in "get_user()"
* and yet we don't want to do any pointers, because that is too much
* of a performance impact. Thus we have a few rather ugly macros here,
* and hide all the ugliness from the user.
*
* The "__xxx" versions of the user access functions are versions that
* do not verify the address space, that must have been done previously
* with a separate "access_ok()" call (this is used when we do multiple
* accesses to the same area of user memory).
*/
extern int __get_user_1(void);
extern int __get_user_2(void);
extern int __get_user_4(void);
extern int __get_user_8(void);
extern int __get_user_bad(void);
#define __get_user_x(size, ret, x, ptr) \
asm volatile("call __get_user_" #size \
: "=a" (ret), "=d" (x) \
: "0" (ptr)) \
/* Careful: we have to cast the result to the type of the pointer
* for sign reasons */
/**
* get_user: - Get a simple variable from user space.
* @x: Variable to store result.
* @ptr: Source address, in user space.
*
* Context: User context only. This function may sleep.
*
* This macro copies a single simple variable from user space to kernel
* space. It supports simple types like char and int, but not larger
* data types like structures or arrays.
*
* @ptr must have pointer-to-simple-variable type, and the result of
* dereferencing @ptr must be assignable to @x without a cast.
*
* Returns zero on success, or -EFAULT on error.
* On error, the variable @x is set to zero.
*/
#ifdef CONFIG_X86_32
#define __get_user_8(__ret_gu, __val_gu, ptr) \
__get_user_x(X, __ret_gu, __val_gu, ptr)
#else
#define __get_user_8(__ret_gu, __val_gu, ptr) \
__get_user_x(8, __ret_gu, __val_gu, ptr)
#endif
#define get_user(x, ptr) \
({ \
int __ret_gu; \
unsigned long __val_gu; \
__chk_user_ptr(ptr); \
might_fault(); \
switch (sizeof(*(ptr))) { \
case 1: \
__get_user_x(1, __ret_gu, __val_gu, ptr); \
break; \
case 2: \
__get_user_x(2, __ret_gu, __val_gu, ptr); \
break; \
case 4: \
__get_user_x(4, __ret_gu, __val_gu, ptr); \
break; \
case 8: \
__get_user_8(__ret_gu, __val_gu, ptr); \
break; \
default: \
__get_user_x(X, __ret_gu, __val_gu, ptr); \
break; \
} \
(x) = (__typeof__(*(ptr)))__val_gu; \
__ret_gu; \
})
#define __put_user_x(size, x, ptr, __ret_pu) \
asm volatile("call __put_user_" #size : "=a" (__ret_pu) \
: "0" ((typeof(*(ptr)))(x)), "c" (ptr) : "ebx")
#ifdef CONFIG_X86_32
#define __put_user_asm_u64(x, addr, err, errret) \
asm volatile("1: movl %%eax,0(%2)\n" \
"2: movl %%edx,4(%2)\n" \
"3:\n" \
".section .fixup,\"ax\"\n" \
"4: movl %3,%0\n" \
" jmp 3b\n" \
".previous\n" \
_ASM_EXTABLE(1b, 4b) \
_ASM_EXTABLE(2b, 4b) \
: "=r" (err) \
: "A" (x), "r" (addr), "i" (errret), "0" (err))
#define __put_user_asm_ex_u64(x, addr) \
asm volatile("1: movl %%eax,0(%1)\n" \
"2: movl %%edx,4(%1)\n" \
"3:\n" \
_ASM_EXTABLE(1b, 2b - 1b) \
_ASM_EXTABLE(2b, 3b - 2b) \
: : "A" (x), "r" (addr))
#define __put_user_x8(x, ptr, __ret_pu) \
asm volatile("call __put_user_8" : "=a" (__ret_pu) \
: "A" ((typeof(*(ptr)))(x)), "c" (ptr) : "ebx")
#else
#define __put_user_asm_u64(x, ptr, retval, errret) \
__put_user_asm(x, ptr, retval, "q", "", "Zr", errret)
#define __put_user_asm_ex_u64(x, addr) \
__put_user_asm_ex(x, addr, "q", "", "Zr")
#define __put_user_x8(x, ptr, __ret_pu) __put_user_x(8, x, ptr, __ret_pu)
#endif
extern void __put_user_bad(void);
/*
* Strange magic calling convention: pointer in %ecx,
* value in %eax(:%edx), return value in %eax. clobbers %rbx
*/
extern void __put_user_1(void);
extern void __put_user_2(void);
extern void __put_user_4(void);
extern void __put_user_8(void);
#ifdef CONFIG_X86_WP_WORKS_OK
/**
* put_user: - Write a simple value into user space.
* @x: Value to copy to user space.
* @ptr: Destination address, in user space.
*
* Context: User context only. This function may sleep.
*
* This macro copies a single simple value from kernel space to user
* space. It supports simple types like char and int, but not larger
* data types like structures or arrays.
*
* @ptr must have pointer-to-simple-variable type, and @x must be assignable
* to the result of dereferencing @ptr.
*
* Returns zero on success, or -EFAULT on error.
*/
#define put_user(x, ptr) \
({ \
int __ret_pu; \
__typeof__(*(ptr)) __pu_val; \
__chk_user_ptr(ptr); \
might_fault(); \
__pu_val = x; \
switch (sizeof(*(ptr))) { \
case 1: \
__put_user_x(1, __pu_val, ptr, __ret_pu); \
break; \
case 2: \
__put_user_x(2, __pu_val, ptr, __ret_pu); \
break; \
case 4: \
__put_user_x(4, __pu_val, ptr, __ret_pu); \
break; \
case 8: \
__put_user_x8(__pu_val, ptr, __ret_pu); \
break; \
default: \
__put_user_x(X, __pu_val, ptr, __ret_pu); \
break; \
} \
__ret_pu; \
})
#define __put_user_size(x, ptr, size, retval, errret) \
do { \
retval = 0; \
__chk_user_ptr(ptr); \
switch (size) { \
case 1: \
__put_user_asm(x, ptr, retval, "b", "b", "iq", errret); \
break; \
case 2: \
__put_user_asm(x, ptr, retval, "w", "w", "ir", errret); \
break; \
case 4: \
__put_user_asm(x, ptr, retval, "l", "k", "ir", errret); \
break; \
case 8: \
__put_user_asm_u64((__typeof__(*ptr))(x), ptr, retval, \
errret); \
break; \
default: \
__put_user_bad(); \
} \
} while (0)
#define __put_user_size_ex(x, ptr, size) \
do { \
__chk_user_ptr(ptr); \
switch (size) { \
case 1: \
__put_user_asm_ex(x, ptr, "b", "b", "iq"); \
break; \
case 2: \
__put_user_asm_ex(x, ptr, "w", "w", "ir"); \
break; \
case 4: \
__put_user_asm_ex(x, ptr, "l", "k", "ir"); \
break; \
case 8: \
__put_user_asm_ex_u64((__typeof__(*ptr))(x), ptr); \
break; \
default: \
__put_user_bad(); \
} \
} while (0)
#else
#define __put_user_size(x, ptr, size, retval, errret) \
do { \
__typeof__(*(ptr))__pus_tmp = x; \
retval = 0; \
\
if (unlikely(__copy_to_user_ll(ptr, &__pus_tmp, size) != 0)) \
retval = errret; \
} while (0)
#define put_user(x, ptr) \
({ \
int __ret_pu; \
__typeof__(*(ptr))__pus_tmp = x; \
__ret_pu = 0; \
if (unlikely(__copy_to_user_ll(ptr, &__pus_tmp, \
sizeof(*(ptr))) != 0)) \
__ret_pu = -EFAULT; \
__ret_pu; \
})
#endif
#ifdef CONFIG_X86_32
#define __get_user_asm_u64(x, ptr, retval, errret) (x) = __get_user_bad()
#define __get_user_asm_ex_u64(x, ptr) (x) = __get_user_bad()
#else
#define __get_user_asm_u64(x, ptr, retval, errret) \
__get_user_asm(x, ptr, retval, "q", "", "=r", errret)
#define __get_user_asm_ex_u64(x, ptr) \
__get_user_asm_ex(x, ptr, "q", "", "=r")
#endif
#define __get_user_size(x, ptr, size, retval, errret) \
do { \
retval = 0; \
__chk_user_ptr(ptr); \
switch (size) { \
case 1: \
__get_user_asm(x, ptr, retval, "b", "b", "=q", errret); \
break; \
case 2: \
__get_user_asm(x, ptr, retval, "w", "w", "=r", errret); \
break; \
case 4: \
__get_user_asm(x, ptr, retval, "l", "k", "=r", errret); \
break; \
case 8: \
__get_user_asm_u64(x, ptr, retval, errret); \
break; \
default: \
(x) = __get_user_bad(); \
} \
} while (0)
#define __get_user_asm(x, addr, err, itype, rtype, ltype, errret) \
asm volatile("1: mov"itype" %2,%"rtype"1\n" \
"2:\n" \
".section .fixup,\"ax\"\n" \
"3: mov %3,%0\n" \
" xor"itype" %"rtype"1,%"rtype"1\n" \
" jmp 2b\n" \
".previous\n" \
_ASM_EXTABLE(1b, 3b) \
: "=r" (err), ltype(x) \
: "m" (__m(addr)), "i" (errret), "0" (err))
#define __get_user_size_ex(x, ptr, size) \
do { \
__chk_user_ptr(ptr); \
switch (size) { \
case 1: \
__get_user_asm_ex(x, ptr, "b", "b", "=q"); \
break; \
case 2: \
__get_user_asm_ex(x, ptr, "w", "w", "=r"); \
break; \
case 4: \
__get_user_asm_ex(x, ptr, "l", "k", "=r"); \
break; \
case 8: \
__get_user_asm_ex_u64(x, ptr); \
break; \
default: \
(x) = __get_user_bad(); \
} \
} while (0)
#define __get_user_asm_ex(x, addr, itype, rtype, ltype) \
asm volatile("1: mov"itype" %1,%"rtype"0\n" \
"2:\n" \
_ASM_EXTABLE(1b, 2b - 1b) \
: ltype(x) : "m" (__m(addr)))
#define __put_user_nocheck(x, ptr, size) \
({ \
int __pu_err; \
__put_user_size((x), (ptr), (size), __pu_err, -EFAULT); \
__pu_err; \
})
#define __get_user_nocheck(x, ptr, size) \
({ \
int __gu_err; \
unsigned long __gu_val; \
__get_user_size(__gu_val, (ptr), (size), __gu_err, -EFAULT); \
(x) = (__force __typeof__(*(ptr)))__gu_val; \
__gu_err; \
})
/* FIXME: this hack is definitely wrong -AK */
struct __large_struct { unsigned long buf[100]; };
#define __m(x) (*(struct __large_struct __user *)(x))
/*
* Tell gcc we read from memory instead of writing: this is because
* we do not write to any memory gcc knows about, so there are no
* aliasing issues.
*/
#define __put_user_asm(x, addr, err, itype, rtype, ltype, errret) \
asm volatile("1: mov"itype" %"rtype"1,%2\n" \
"2:\n" \
".section .fixup,\"ax\"\n" \
"3: mov %3,%0\n" \
" jmp 2b\n" \
".previous\n" \
_ASM_EXTABLE(1b, 3b) \
: "=r"(err) \
: ltype(x), "m" (__m(addr)), "i" (errret), "0" (err))
#define __put_user_asm_ex(x, addr, itype, rtype, ltype) \
asm volatile("1: mov"itype" %"rtype"0,%1\n" \
"2:\n" \
_ASM_EXTABLE(1b, 2b - 1b) \
: : ltype(x), "m" (__m(addr)))
/*
* uaccess_try and catch
*/
#define uaccess_try do { \
int prev_err = current_thread_info()->uaccess_err; \
current_thread_info()->uaccess_err = 0; \
barrier();
#define uaccess_catch(err) \
(err) |= current_thread_info()->uaccess_err; \
current_thread_info()->uaccess_err = prev_err; \
} while (0)
/**
* __get_user: - Get a simple variable from user space, with less checking.
* @x: Variable to store result.
* @ptr: Source address, in user space.
*
* Context: User context only. This function may sleep.
*
* This macro copies a single simple variable from user space to kernel
* space. It supports simple types like char and int, but not larger
* data types like structures or arrays.
*
* @ptr must have pointer-to-simple-variable type, and the result of
* dereferencing @ptr must be assignable to @x without a cast.
*
* Caller must check the pointer with access_ok() before calling this
* function.
*
* Returns zero on success, or -EFAULT on error.
* On error, the variable @x is set to zero.
*/
#define __get_user(x, ptr) \
__get_user_nocheck((x), (ptr), sizeof(*(ptr)))
/**
* __put_user: - Write a simple value into user space, with less checking.
* @x: Value to copy to user space.
* @ptr: Destination address, in user space.
*
* Context: User context only. This function may sleep.
*
* This macro copies a single simple value from kernel space to user
* space. It supports simple types like char and int, but not larger
* data types like structures or arrays.
*
* @ptr must have pointer-to-simple-variable type, and @x must be assignable
* to the result of dereferencing @ptr.
*
* Caller must check the pointer with access_ok() before calling this
* function.
*
* Returns zero on success, or -EFAULT on error.
*/
#define __put_user(x, ptr) \
__put_user_nocheck((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)))
#define __get_user_unaligned __get_user
#define __put_user_unaligned __put_user
/*
* {get|put}_user_try and catch
*
* get_user_try {
* get_user_ex(...);
* } get_user_catch(err)
*/
#define get_user_try uaccess_try
#define get_user_catch(err) uaccess_catch(err)
#define get_user_ex(x, ptr) do { \
unsigned long __gue_val; \
__get_user_size_ex((__gue_val), (ptr), (sizeof(*(ptr)))); \
(x) = (__force __typeof__(*(ptr)))__gue_val; \
} while (0)
#ifdef CONFIG_X86_WP_WORKS_OK
#define put_user_try uaccess_try
#define put_user_catch(err) uaccess_catch(err)
#define put_user_ex(x, ptr) \
__put_user_size_ex((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)))
#else /* !CONFIG_X86_WP_WORKS_OK */
#define put_user_try do { \
int __uaccess_err = 0;
#define put_user_catch(err) \
(err) |= __uaccess_err; \
} while (0)
#define put_user_ex(x, ptr) do { \
__uaccess_err |= __put_user(x, ptr); \
} while (0)
#endif /* CONFIG_X86_WP_WORKS_OK */
/*
* movsl can be slow when source and dest are not both 8-byte aligned
*/
#ifdef CONFIG_X86_INTEL_USERCOPY
extern struct movsl_mask {
int mask;
} ____cacheline_aligned_in_smp movsl_mask;
#endif
#define ARCH_HAS_NOCACHE_UACCESS 1
#ifdef CONFIG_X86_32
# include "uaccess_32.h"
#else
# define ARCH_HAS_SEARCH_EXTABLE
# include "uaccess_64.h"
#endif
#endif /* _ASM_X86_UACCESS_H */
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