Linux lhjmq-records 5.15.0-118-generic #128-Ubuntu SMP Fri Jul 5 09:28:59 UTC 2024 x86_64
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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __LINUX_UACCESS_H__
#define __LINUX_UACCESS_H__
#include <linux/fault-inject-usercopy.h>
#include <linux/instrumented.h>
#include <linux/minmax.h>
#include <linux/sched.h>
#include <linux/thread_info.h>
#include <asm/uaccess.h>
#ifdef CONFIG_SET_FS
/*
* Force the uaccess routines to be wired up for actual userspace access,
* overriding any possible set_fs(KERNEL_DS) still lingering around. Undone
* using force_uaccess_end below.
*/
static inline mm_segment_t force_uaccess_begin(void)
{
mm_segment_t fs = get_fs();
set_fs(USER_DS);
return fs;
}
static inline void force_uaccess_end(mm_segment_t oldfs)
{
set_fs(oldfs);
}
#else /* CONFIG_SET_FS */
typedef struct {
/* empty dummy */
} mm_segment_t;
#ifndef TASK_SIZE_MAX
#define TASK_SIZE_MAX TASK_SIZE
#endif
#define uaccess_kernel() (false)
#define user_addr_max() (TASK_SIZE_MAX)
static inline mm_segment_t force_uaccess_begin(void)
{
return (mm_segment_t) { };
}
static inline void force_uaccess_end(mm_segment_t oldfs)
{
}
#endif /* CONFIG_SET_FS */
/*
* Architectures should provide two primitives (raw_copy_{to,from}_user())
* and get rid of their private instances of copy_{to,from}_user() and
* __copy_{to,from}_user{,_inatomic}().
*
* raw_copy_{to,from}_user(to, from, size) should copy up to size bytes and
* return the amount left to copy. They should assume that access_ok() has
* already been checked (and succeeded); they should *not* zero-pad anything.
* No KASAN or object size checks either - those belong here.
*
* Both of these functions should attempt to copy size bytes starting at from
* into the area starting at to. They must not fetch or store anything
* outside of those areas. Return value must be between 0 (everything
* copied successfully) and size (nothing copied).
*
* If raw_copy_{to,from}_user(to, from, size) returns N, size - N bytes starting
* at to must become equal to the bytes fetched from the corresponding area
* starting at from. All data past to + size - N must be left unmodified.
*
* If copying succeeds, the return value must be 0. If some data cannot be
* fetched, it is permitted to copy less than had been fetched; the only
* hard requirement is that not storing anything at all (i.e. returning size)
* should happen only when nothing could be copied. In other words, you don't
* have to squeeze as much as possible - it is allowed, but not necessary.
*
* For raw_copy_from_user() to always points to kernel memory and no faults
* on store should happen. Interpretation of from is affected by set_fs().
* For raw_copy_to_user() it's the other way round.
*
* Both can be inlined - it's up to architectures whether it wants to bother
* with that. They should not be used directly; they are used to implement
* the 6 functions (copy_{to,from}_user(), __copy_{to,from}_user_inatomic())
* that are used instead. Out of those, __... ones are inlined. Plain
* copy_{to,from}_user() might or might not be inlined. If you want them
* inlined, have asm/uaccess.h define INLINE_COPY_{TO,FROM}_USER.
*
* NOTE: only copy_from_user() zero-pads the destination in case of short copy.
* Neither __copy_from_user() nor __copy_from_user_inatomic() zero anything
* at all; their callers absolutely must check the return value.
*
* Biarch ones should also provide raw_copy_in_user() - similar to the above,
* but both source and destination are __user pointers (affected by set_fs()
* as usual) and both source and destination can trigger faults.
*/
static __always_inline __must_check unsigned long
__copy_from_user_inatomic(void *to, const void __user *from, unsigned long n)
{
instrument_copy_from_user(to, from, n);
check_object_size(to, n, false);
return raw_copy_from_user(to, from, n);
}
static __always_inline __must_check unsigned long
__copy_from_user(void *to, const void __user *from, unsigned long n)
{
might_fault();
if (should_fail_usercopy())
return n;
instrument_copy_from_user(to, from, n);
check_object_size(to, n, false);
return raw_copy_from_user(to, from, n);
}
/**
* __copy_to_user_inatomic: - Copy a block of data into user space, with less checking.
* @to: Destination address, in user space.
* @from: Source address, in kernel space.
* @n: Number of bytes to copy.
*
* Context: User context only.
*
* Copy data from kernel space to user space. Caller must check
* the specified block with access_ok() before calling this function.
* The caller should also make sure he pins the user space address
* so that we don't result in page fault and sleep.
*/
static __always_inline __must_check unsigned long
__copy_to_user_inatomic(void __user *to, const void *from, unsigned long n)
{
if (should_fail_usercopy())
return n;
instrument_copy_to_user(to, from, n);
check_object_size(from, n, true);
return raw_copy_to_user(to, from, n);
}
static __always_inline __must_check unsigned long
__copy_to_user(void __user *to, const void *from, unsigned long n)
{
might_fault();
if (should_fail_usercopy())
return n;
instrument_copy_to_user(to, from, n);
check_object_size(from, n, true);
return raw_copy_to_user(to, from, n);
}
#ifdef INLINE_COPY_FROM_USER
static inline __must_check unsigned long
_copy_from_user(void *to, const void __user *from, unsigned long n)
{
unsigned long res = n;
might_fault();
if (!should_fail_usercopy() && likely(access_ok(from, n))) {
instrument_copy_from_user(to, from, n);
res = raw_copy_from_user(to, from, n);
}
if (unlikely(res))
memset(to + (n - res), 0, res);
return res;
}
#else
extern __must_check unsigned long
_copy_from_user(void *, const void __user *, unsigned long);
#endif
#ifdef INLINE_COPY_TO_USER
static inline __must_check unsigned long
_copy_to_user(void __user *to, const void *from, unsigned long n)
{
might_fault();
if (should_fail_usercopy())
return n;
if (access_ok(to, n)) {
instrument_copy_to_user(to, from, n);
n = raw_copy_to_user(to, from, n);
}
return n;
}
#else
extern __must_check unsigned long
_copy_to_user(void __user *, const void *, unsigned long);
#endif
static __always_inline unsigned long __must_check
copy_from_user(void *to, const void __user *from, unsigned long n)
{
if (likely(check_copy_size(to, n, false)))
n = _copy_from_user(to, from, n);
return n;
}
static __always_inline unsigned long __must_check
copy_to_user(void __user *to, const void *from, unsigned long n)
{
if (likely(check_copy_size(from, n, true)))
n = _copy_to_user(to, from, n);
return n;
}
#ifndef copy_mc_to_kernel
/*
* Without arch opt-in this generic copy_mc_to_kernel() will not handle
* #MC (or arch equivalent) during source read.
*/
static inline unsigned long __must_check
copy_mc_to_kernel(void *dst, const void *src, size_t cnt)
{
memcpy(dst, src, cnt);
return 0;
}
#endif
static __always_inline void pagefault_disabled_inc(void)
{
current->pagefault_disabled++;
}
static __always_inline void pagefault_disabled_dec(void)
{
current->pagefault_disabled--;
}
/*
* These routines enable/disable the pagefault handler. If disabled, it will
* not take any locks and go straight to the fixup table.
*
* User access methods will not sleep when called from a pagefault_disabled()
* environment.
*/
static inline void pagefault_disable(void)
{
pagefault_disabled_inc();
/*
* make sure to have issued the store before a pagefault
* can hit.
*/
barrier();
}
static inline void pagefault_enable(void)
{
/*
* make sure to issue those last loads/stores before enabling
* the pagefault handler again.
*/
barrier();
pagefault_disabled_dec();
}
/*
* Is the pagefault handler disabled? If so, user access methods will not sleep.
*/
static inline bool pagefault_disabled(void)
{
return current->pagefault_disabled != 0;
}
/*
* The pagefault handler is in general disabled by pagefault_disable() or
* when in irq context (via in_atomic()).
*
* This function should only be used by the fault handlers. Other users should
* stick to pagefault_disabled().
* Please NEVER use preempt_disable() to disable the fault handler. With
* !CONFIG_PREEMPT_COUNT, this is like a NOP. So the handler won't be disabled.
* in_atomic() will report different values based on !CONFIG_PREEMPT_COUNT.
*/
#define faulthandler_disabled() (pagefault_disabled() || in_atomic())
#ifndef ARCH_HAS_NOCACHE_UACCESS
static inline __must_check unsigned long
__copy_from_user_inatomic_nocache(void *to, const void __user *from,
unsigned long n)
{
return __copy_from_user_inatomic(to, from, n);
}
#endif /* ARCH_HAS_NOCACHE_UACCESS */
extern __must_check int check_zeroed_user(const void __user *from, size_t size);
/**
* copy_struct_from_user: copy a struct from userspace
* @dst: Destination address, in kernel space. This buffer must be @ksize
* bytes long.
* @ksize: Size of @dst struct.
* @src: Source address, in userspace.
* @usize: (Alleged) size of @src struct.
*
* Copies a struct from userspace to kernel space, in a way that guarantees
* backwards-compatibility for struct syscall arguments (as long as future
* struct extensions are made such that all new fields are *appended* to the
* old struct, and zeroed-out new fields have the same meaning as the old
* struct).
*
* @ksize is just sizeof(*dst), and @usize should've been passed by userspace.
* The recommended usage is something like the following:
*
* SYSCALL_DEFINE2(foobar, const struct foo __user *, uarg, size_t, usize)
* {
* int err;
* struct foo karg = {};
*
* if (usize > PAGE_SIZE)
* return -E2BIG;
* if (usize < FOO_SIZE_VER0)
* return -EINVAL;
*
* err = copy_struct_from_user(&karg, sizeof(karg), uarg, usize);
* if (err)
* return err;
*
* // ...
* }
*
* There are three cases to consider:
* * If @usize == @ksize, then it's copied verbatim.
* * If @usize < @ksize, then the userspace has passed an old struct to a
* newer kernel. The rest of the trailing bytes in @dst (@ksize - @usize)
* are to be zero-filled.
* * If @usize > @ksize, then the userspace has passed a new struct to an
* older kernel. The trailing bytes unknown to the kernel (@usize - @ksize)
* are checked to ensure they are zeroed, otherwise -E2BIG is returned.
*
* Returns (in all cases, some data may have been copied):
* * -E2BIG: (@usize > @ksize) and there are non-zero trailing bytes in @src.
* * -EFAULT: access to userspace failed.
*/
static __always_inline __must_check int
copy_struct_from_user(void *dst, size_t ksize, const void __user *src,
size_t usize)
{
size_t size = min(ksize, usize);
size_t rest = max(ksize, usize) - size;
/* Double check if ksize is larger than a known object size. */
if (WARN_ON_ONCE(ksize > __builtin_object_size(dst, 1)))
return -E2BIG;
/* Deal with trailing bytes. */
if (usize < ksize) {
memset(dst + size, 0, rest);
} else if (usize > ksize) {
int ret = check_zeroed_user(src + size, rest);
if (ret <= 0)
return ret ?: -E2BIG;
}
/* Copy the interoperable parts of the struct. */
if (copy_from_user(dst, src, size))
return -EFAULT;
return 0;
}
bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size);
long copy_from_kernel_nofault(void *dst, const void *src, size_t size);
long notrace copy_to_kernel_nofault(void *dst, const void *src, size_t size);
long copy_from_user_nofault(void *dst, const void __user *src, size_t size);
long notrace copy_to_user_nofault(void __user *dst, const void *src,
size_t size);
long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr,
long count);
long strncpy_from_user_nofault(char *dst, const void __user *unsafe_addr,
long count);
long strnlen_user_nofault(const void __user *unsafe_addr, long count);
/**
* get_kernel_nofault(): safely attempt to read from a location
* @val: read into this variable
* @ptr: address to read from
*
* Returns 0 on success, or -EFAULT.
*/
#define get_kernel_nofault(val, ptr) ({ \
const typeof(val) *__gk_ptr = (ptr); \
copy_from_kernel_nofault(&(val), __gk_ptr, sizeof(val));\
})
#ifndef user_access_begin
#define user_access_begin(ptr,len) access_ok(ptr, len)
#define user_access_end() do { } while (0)
#define unsafe_op_wrap(op, err) do { if (unlikely(op)) goto err; } while (0)
#define unsafe_get_user(x,p,e) unsafe_op_wrap(__get_user(x,p),e)
#define unsafe_put_user(x,p,e) unsafe_op_wrap(__put_user(x,p),e)
#define unsafe_copy_to_user(d,s,l,e) unsafe_op_wrap(__copy_to_user(d,s,l),e)
#define unsafe_copy_from_user(d,s,l,e) unsafe_op_wrap(__copy_from_user(d,s,l),e)
static inline unsigned long user_access_save(void) { return 0UL; }
static inline void user_access_restore(unsigned long flags) { }
#endif
#ifndef user_write_access_begin
#define user_write_access_begin user_access_begin
#define user_write_access_end user_access_end
#endif
#ifndef user_read_access_begin
#define user_read_access_begin user_access_begin
#define user_read_access_end user_access_end
#endif
#ifdef CONFIG_HARDENED_USERCOPY
void usercopy_warn(const char *name, const char *detail, bool to_user,
unsigned long offset, unsigned long len);
void __noreturn usercopy_abort(const char *name, const char *detail,
bool to_user, unsigned long offset,
unsigned long len);
#endif
#endif /* __LINUX_UACCESS_H__ */
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