mm/maccess.c - third_party/kernel - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Access kernel or user memory without faulting.
  */
 #include <linux/export.h>
 #include <linux/mm.h>
 #include <linux/uaccess.h>

 bool __weak copy_from_kernel_nofault_allowed(const void *unsafe_src,
 		size_t size)
 {
 	return true;
 }

 #ifdef HAVE_GET_KERNEL_NOFAULT

 #define copy_from_kernel_nofault_loop(dst, src, len, type, err_label)	\
 	while (len >= sizeof(type)) {					\
 		__get_kernel_nofault(dst, src, type, err_label);		\
 		dst += sizeof(type);					\
 		src += sizeof(type);					\
 		len -= sizeof(type);					\
 	}

 long copy_from_kernel_nofault(void *dst, const void *src, size_t size)
 {
 	unsigned long align = 0;

 	if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
 		align = (unsigned long)dst | (unsigned long)src;

 	if (!copy_from_kernel_nofault_allowed(src, size))
 		return -ERANGE;

 	pagefault_disable();
 	if (!(align & 7))
 		copy_from_kernel_nofault_loop(dst, src, size, u64, Efault);
 	if (!(align & 3))
 		copy_from_kernel_nofault_loop(dst, src, size, u32, Efault);
 	if (!(align & 1))
 		copy_from_kernel_nofault_loop(dst, src, size, u16, Efault);
 	copy_from_kernel_nofault_loop(dst, src, size, u8, Efault);
 	pagefault_enable();
 	return 0;
 Efault:
 	pagefault_enable();
 	return -EFAULT;
 }
 EXPORT_SYMBOL_GPL(copy_from_kernel_nofault);

 #define copy_to_kernel_nofault_loop(dst, src, len, type, err_label)	\
 	while (len >= sizeof(type)) {					\
 		__put_kernel_nofault(dst, src, type, err_label);		\
 		dst += sizeof(type);					\
 		src += sizeof(type);					\
 		len -= sizeof(type);					\
 	}

 long copy_to_kernel_nofault(void *dst, const void *src, size_t size)
 {
 	unsigned long align = 0;

 	if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
 		align = (unsigned long)dst | (unsigned long)src;

 	pagefault_disable();
 	if (!(align & 7))
 		copy_to_kernel_nofault_loop(dst, src, size, u64, Efault);
 	if (!(align & 3))
 		copy_to_kernel_nofault_loop(dst, src, size, u32, Efault);
 	if (!(align & 1))
 		copy_to_kernel_nofault_loop(dst, src, size, u16, Efault);
 	copy_to_kernel_nofault_loop(dst, src, size, u8, Efault);
 	pagefault_enable();
 	return 0;
 Efault:
 	pagefault_enable();
 	return -EFAULT;
 }

 long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count)
 {
 	const void *src = unsafe_addr;

 	if (unlikely(count <= 0))
 		return 0;
 	if (!copy_from_kernel_nofault_allowed(unsafe_addr, count))
 		return -ERANGE;

 	pagefault_disable();
 	do {
 		__get_kernel_nofault(dst, src, u8, Efault);
 		dst++;
 		src++;
 	} while (dst[-1] && src - unsafe_addr < count);
 	pagefault_enable();

 	dst[-1] = '\0';
 	return src - unsafe_addr;
 Efault:
 	pagefault_enable();
 	dst[0] = '\0';
 	return -EFAULT;
 }
 #else /* HAVE_GET_KERNEL_NOFAULT */
 /**
  * copy_from_kernel_nofault(): safely attempt to read from kernel-space
  * @dst: pointer to the buffer that shall take the data
  * @src: address to read from
  * @size: size of the data chunk
  *
  * Safely read from kernel address @src to the buffer at @dst.  If a kernel
  * fault happens, handle that and return -EFAULT.  If @src is not a valid kernel
  * address, return -ERANGE.
  *
  * We ensure that the copy_from_user is executed in atomic context so that
  * do_page_fault() doesn't attempt to take mmap_lock.  This makes
  * copy_from_kernel_nofault() suitable for use within regions where the caller
  * already holds mmap_lock, or other locks which nest inside mmap_lock.
  */
 long copy_from_kernel_nofault(void *dst, const void *src, size_t size)
 {
 	long ret;
 	mm_segment_t old_fs = get_fs();

 	if (!copy_from_kernel_nofault_allowed(src, size))
 		return -ERANGE;

 	set_fs(KERNEL_DS);
 	pagefault_disable();
 	ret = __copy_from_user_inatomic(dst, (__force const void __user *)src,
 			size);
 	pagefault_enable();
 	set_fs(old_fs);

 	if (ret)
 		return -EFAULT;
 	return 0;
 }
 EXPORT_SYMBOL_GPL(copy_from_kernel_nofault);

 /**
  * copy_to_kernel_nofault(): safely attempt to write to a location
  * @dst: address to write to
  * @src: pointer to the data that shall be written
  * @size: size of the data chunk
  *
  * Safely write to address @dst from the buffer at @src.  If a kernel fault
  * happens, handle that and return -EFAULT.
  */
 long copy_to_kernel_nofault(void *dst, const void *src, size_t size)
 {
 	long ret;
 	mm_segment_t old_fs = get_fs();

 	set_fs(KERNEL_DS);
 	pagefault_disable();
 	ret = __copy_to_user_inatomic((__force void __user *)dst, src, size);
 	pagefault_enable();
 	set_fs(old_fs);

 	if (ret)
 		return -EFAULT;
 	return 0;
 }

 /**
  * strncpy_from_kernel_nofault: - Copy a NUL terminated string from unsafe
  *				 address.
  * @dst:   Destination address, in kernel space.  This buffer must be at
  *         least @count bytes long.
  * @unsafe_addr: Unsafe address.
  * @count: Maximum number of bytes to copy, including the trailing NUL.
  *
  * Copies a NUL-terminated string from unsafe address to kernel buffer.
  *
  * On success, returns the length of the string INCLUDING the trailing NUL.
  *
  * If access fails, returns -EFAULT (some data may have been copied and the
  * trailing NUL added).  If @unsafe_addr is not a valid kernel address, return
  * -ERANGE.
  *
  * If @count is smaller than the length of the string, copies @count-1 bytes,
  * sets the last byte of @dst buffer to NUL and returns @count.
  */
 long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count)
 {
 	mm_segment_t old_fs = get_fs();
 	const void *src = unsafe_addr;
 	long ret;

 	if (unlikely(count <= 0))
 		return 0;
 	if (!copy_from_kernel_nofault_allowed(unsafe_addr, count))
 		return -ERANGE;

 	set_fs(KERNEL_DS);
 	pagefault_disable();

 	do {
 		ret = __get_user(*dst++, (const char __user __force *)src++);
 	} while (dst[-1] && ret == 0 && src - unsafe_addr < count);

 	dst[-1] = '\0';
 	pagefault_enable();
 	set_fs(old_fs);

 	return ret ? -EFAULT : src - unsafe_addr;
 }
 #endif /* HAVE_GET_KERNEL_NOFAULT */

 /**
  * copy_from_user_nofault(): safely attempt to read from a user-space location
  * @dst: pointer to the buffer that shall take the data
  * @src: address to read from. This must be a user address.
  * @size: size of the data chunk
  *
  * Safely read from user address @src to the buffer at @dst. If a kernel fault
  * happens, handle that and return -EFAULT.
  */
 long copy_from_user_nofault(void *dst, const void __user *src, size_t size)
 {
 	long ret = -EFAULT;
 	mm_segment_t old_fs = force_uaccess_begin();

 	if (access_ok(src, size)) {
 		pagefault_disable();
 		ret = __copy_from_user_inatomic(dst, src, size);
 		pagefault_enable();
 	}
 	force_uaccess_end(old_fs);

 	if (ret)
 		return -EFAULT;
 	return 0;
 }
 EXPORT_SYMBOL_GPL(copy_from_user_nofault);

 /**
  * copy_to_user_nofault(): safely attempt to write to a user-space location
  * @dst: address to write to
  * @src: pointer to the data that shall be written
  * @size: size of the data chunk
  *
  * Safely write to address @dst from the buffer at @src.  If a kernel fault
  * happens, handle that and return -EFAULT.
  */
 long copy_to_user_nofault(void __user *dst, const void *src, size_t size)
 {
 	long ret = -EFAULT;
 	mm_segment_t old_fs = force_uaccess_begin();

 	if (access_ok(dst, size)) {
 		pagefault_disable();
 		ret = __copy_to_user_inatomic(dst, src, size);
 		pagefault_enable();
 	}
 	force_uaccess_end(old_fs);

 	if (ret)
 		return -EFAULT;
 	return 0;
 }
 EXPORT_SYMBOL_GPL(copy_to_user_nofault);

 /**
  * strncpy_from_user_nofault: - Copy a NUL terminated string from unsafe user
  *				address.
  * @dst:   Destination address, in kernel space.  This buffer must be at
  *         least @count bytes long.
  * @unsafe_addr: Unsafe user address.
  * @count: Maximum number of bytes to copy, including the trailing NUL.
  *
  * Copies a NUL-terminated string from unsafe user address to kernel buffer.
  *
  * On success, returns the length of the string INCLUDING the trailing NUL.
  *
  * If access fails, returns -EFAULT (some data may have been copied
  * and the trailing NUL added).
  *
  * If @count is smaller than the length of the string, copies @count-1 bytes,
  * sets the last byte of @dst buffer to NUL and returns @count.
  */
 long strncpy_from_user_nofault(char *dst, const void __user *unsafe_addr,
 			      long count)
 {
 	mm_segment_t old_fs;
 	long ret;

 	if (unlikely(count <= 0))
 		return 0;

 	old_fs = force_uaccess_begin();
 	pagefault_disable();
 	ret = strncpy_from_user(dst, unsafe_addr, count);
 	pagefault_enable();
 	force_uaccess_end(old_fs);

 	if (ret >= count) {
 		ret = count;
 		dst[ret - 1] = '\0';
 	} else if (ret > 0) {
 		ret++;
 	}

 	return ret;
 }

 /**
  * strnlen_user_nofault: - Get the size of a user string INCLUDING final NUL.
  * @unsafe_addr: The string to measure.
  * @count: Maximum count (including NUL)
  *
  * Get the size of a NUL-terminated string in user space without pagefault.
  *
  * Returns the size of the string INCLUDING the terminating NUL.
  *
  * If the string is too long, returns a number larger than @count. User
  * has to check the return value against "> count".
  * On exception (or invalid count), returns 0.
  *
  * Unlike strnlen_user, this can be used from IRQ handler etc. because
  * it disables pagefaults.
  */
 long strnlen_user_nofault(const void __user *unsafe_addr, long count)
 {
 	mm_segment_t old_fs;
 	int ret;

 	old_fs = force_uaccess_begin();
 	pagefault_disable();
 	ret = strnlen_user(unsafe_addr, count);
 	pagefault_enable();
 	force_uaccess_end(old_fs);

 	return ret;
 }
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Access kernel or user memory without faulting.
	*/
	#include <linux/export.h>
	#include <linux/mm.h>
	#include <linux/uaccess.h>

	bool __weak copy_from_kernel_nofault_allowed(const void *unsafe_src,
	size_t size)
	{
	return true;
	}

	#ifdef HAVE_GET_KERNEL_NOFAULT

	#define copy_from_kernel_nofault_loop(dst, src, len, type, err_label) \
	while (len >= sizeof(type)) { \
	__get_kernel_nofault(dst, src, type, err_label); \
	dst += sizeof(type); \
	src += sizeof(type); \
	len -= sizeof(type); \
	}

	long copy_from_kernel_nofault(void dst, const void src, size_t size)
	{
	unsigned long align = 0;

	if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
	align = (unsigned long)dst \| (unsigned long)src;

	if (!copy_from_kernel_nofault_allowed(src, size))
	return -ERANGE;

	pagefault_disable();
	if (!(align & 7))
	copy_from_kernel_nofault_loop(dst, src, size, u64, Efault);
	if (!(align & 3))
	copy_from_kernel_nofault_loop(dst, src, size, u32, Efault);
	if (!(align & 1))
	copy_from_kernel_nofault_loop(dst, src, size, u16, Efault);
	copy_from_kernel_nofault_loop(dst, src, size, u8, Efault);
	pagefault_enable();
	return 0;
	Efault:
	pagefault_enable();
	return -EFAULT;
	}
	EXPORT_SYMBOL_GPL(copy_from_kernel_nofault);

	#define copy_to_kernel_nofault_loop(dst, src, len, type, err_label) \
	while (len >= sizeof(type)) { \
	__put_kernel_nofault(dst, src, type, err_label); \
	dst += sizeof(type); \
	src += sizeof(type); \
	len -= sizeof(type); \
	}

	long copy_to_kernel_nofault(void dst, const void src, size_t size)
	{
	unsigned long align = 0;

	if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
	align = (unsigned long)dst \| (unsigned long)src;

	pagefault_disable();
	if (!(align & 7))
	copy_to_kernel_nofault_loop(dst, src, size, u64, Efault);
	if (!(align & 3))
	copy_to_kernel_nofault_loop(dst, src, size, u32, Efault);
	if (!(align & 1))
	copy_to_kernel_nofault_loop(dst, src, size, u16, Efault);
	copy_to_kernel_nofault_loop(dst, src, size, u8, Efault);
	pagefault_enable();
	return 0;
	Efault:
	pagefault_enable();
	return -EFAULT;
	}

	long strncpy_from_kernel_nofault(char dst, const void unsafe_addr, long count)
	{
	const void *src = unsafe_addr;

	if (unlikely(count <= 0))
	return 0;
	if (!copy_from_kernel_nofault_allowed(unsafe_addr, count))
	return -ERANGE;

	pagefault_disable();
	do {
	__get_kernel_nofault(dst, src, u8, Efault);
	dst++;
	src++;
	} while (dst[-1] && src - unsafe_addr < count);
	pagefault_enable();

	dst[-1] = '\0';
	return src - unsafe_addr;
	Efault:
	pagefault_enable();
	dst[0] = '\0';
	return -EFAULT;
	}
	#else /* HAVE_GET_KERNEL_NOFAULT */
	/**
	* copy_from_kernel_nofault(): safely attempt to read from kernel-space
	* @dst: pointer to the buffer that shall take the data
	* @src: address to read from
	* @size: size of the data chunk
	*
	* Safely read from kernel address @src to the buffer at @dst. If a kernel
	* fault happens, handle that and return -EFAULT. If @src is not a valid kernel
	* address, return -ERANGE.
	*
	* We ensure that the copy_from_user is executed in atomic context so that
	* do_page_fault() doesn't attempt to take mmap_lock. This makes
	* copy_from_kernel_nofault() suitable for use within regions where the caller
	* already holds mmap_lock, or other locks which nest inside mmap_lock.
	*/
	long copy_from_kernel_nofault(void dst, const void src, size_t size)
	{
	long ret;
	mm_segment_t old_fs = get_fs();

	if (!copy_from_kernel_nofault_allowed(src, size))
	return -ERANGE;

	set_fs(KERNEL_DS);
	pagefault_disable();
	ret = __copy_from_user_inatomic(dst, (__force const void __user *)src,
	size);
	pagefault_enable();
	set_fs(old_fs);

	if (ret)
	return -EFAULT;
	return 0;
	}
	EXPORT_SYMBOL_GPL(copy_from_kernel_nofault);

	/**
	* copy_to_kernel_nofault(): safely attempt to write to a location
	* @dst: address to write to
	* @src: pointer to the data that shall be written
	* @size: size of the data chunk
	*
	* Safely write to address @dst from the buffer at @src. If a kernel fault
	* happens, handle that and return -EFAULT.
	*/
	long copy_to_kernel_nofault(void dst, const void src, size_t size)
	{
	long ret;
	mm_segment_t old_fs = get_fs();

	set_fs(KERNEL_DS);
	pagefault_disable();
	ret = __copy_to_user_inatomic((__force void __user *)dst, src, size);
	pagefault_enable();
	set_fs(old_fs);

	if (ret)
	return -EFAULT;
	return 0;
	}

	/**
	* strncpy_from_kernel_nofault: - Copy a NUL terminated string from unsafe
	* address.
	* @dst: Destination address, in kernel space. This buffer must be at
	* least @count bytes long.
	* @unsafe_addr: Unsafe address.
	* @count: Maximum number of bytes to copy, including the trailing NUL.
	*
	* Copies a NUL-terminated string from unsafe address to kernel buffer.
	*
	* On success, returns the length of the string INCLUDING the trailing NUL.
	*
	* If access fails, returns -EFAULT (some data may have been copied and the
	* trailing NUL added). If @unsafe_addr is not a valid kernel address, return
	* -ERANGE.
	*
	* If @count is smaller than the length of the string, copies @count-1 bytes,
	* sets the last byte of @dst buffer to NUL and returns @count.
	*/
	long strncpy_from_kernel_nofault(char dst, const void unsafe_addr, long count)
	{
	mm_segment_t old_fs = get_fs();
	const void *src = unsafe_addr;
	long ret;

	if (unlikely(count <= 0))
	return 0;
	if (!copy_from_kernel_nofault_allowed(unsafe_addr, count))
	return -ERANGE;

	set_fs(KERNEL_DS);
	pagefault_disable();

	do {
	ret = __get_user(dst++, (const char __user __force )src++);
	} while (dst[-1] && ret == 0 && src - unsafe_addr < count);

	dst[-1] = '\0';
	pagefault_enable();
	set_fs(old_fs);

	return ret ? -EFAULT : src - unsafe_addr;
	}
	#endif /* HAVE_GET_KERNEL_NOFAULT */

	/**
	* copy_from_user_nofault(): safely attempt to read from a user-space location
	* @dst: pointer to the buffer that shall take the data
	* @src: address to read from. This must be a user address.
	* @size: size of the data chunk
	*
	* Safely read from user address @src to the buffer at @dst. If a kernel fault
	* happens, handle that and return -EFAULT.
	*/
	long copy_from_user_nofault(void dst, const void __user src, size_t size)
	{
	long ret = -EFAULT;
	mm_segment_t old_fs = force_uaccess_begin();

	if (access_ok(src, size)) {
	pagefault_disable();
	ret = __copy_from_user_inatomic(dst, src, size);
	pagefault_enable();
	}
	force_uaccess_end(old_fs);

	if (ret)
	return -EFAULT;
	return 0;
	}
	EXPORT_SYMBOL_GPL(copy_from_user_nofault);

	/**
	* copy_to_user_nofault(): safely attempt to write to a user-space location
	* @dst: address to write to
	* @src: pointer to the data that shall be written
	* @size: size of the data chunk
	*
	* Safely write to address @dst from the buffer at @src. If a kernel fault
	* happens, handle that and return -EFAULT.
	*/
	long copy_to_user_nofault(void __user dst, const void src, size_t size)
	{
	long ret = -EFAULT;
	mm_segment_t old_fs = force_uaccess_begin();

	if (access_ok(dst, size)) {
	pagefault_disable();
	ret = __copy_to_user_inatomic(dst, src, size);
	pagefault_enable();
	}
	force_uaccess_end(old_fs);

	if (ret)
	return -EFAULT;
	return 0;
	}
	EXPORT_SYMBOL_GPL(copy_to_user_nofault);

	/**
	* strncpy_from_user_nofault: - Copy a NUL terminated string from unsafe user
	* address.
	* @dst: Destination address, in kernel space. This buffer must be at
	* least @count bytes long.
	* @unsafe_addr: Unsafe user address.
	* @count: Maximum number of bytes to copy, including the trailing NUL.
	*
	* Copies a NUL-terminated string from unsafe user address to kernel buffer.
	*
	* On success, returns the length of the string INCLUDING the trailing NUL.
	*
	* If access fails, returns -EFAULT (some data may have been copied
	* and the trailing NUL added).
	*
	* If @count is smaller than the length of the string, copies @count-1 bytes,
	* sets the last byte of @dst buffer to NUL and returns @count.
	*/
	long strncpy_from_user_nofault(char dst, const void __user unsafe_addr,
	long count)
	{
	mm_segment_t old_fs;
	long ret;

	if (unlikely(count <= 0))
	return 0;

	old_fs = force_uaccess_begin();
	pagefault_disable();
	ret = strncpy_from_user(dst, unsafe_addr, count);
	pagefault_enable();
	force_uaccess_end(old_fs);

	if (ret >= count) {
	ret = count;
	dst[ret - 1] = '\0';
	} else if (ret > 0) {
	ret++;
	}

	return ret;
	}

	/**
	* strnlen_user_nofault: - Get the size of a user string INCLUDING final NUL.
	* @unsafe_addr: The string to measure.
	* @count: Maximum count (including NUL)
	*
	* Get the size of a NUL-terminated string in user space without pagefault.
	*
	* Returns the size of the string INCLUDING the terminating NUL.
	*
	* If the string is too long, returns a number larger than @count. User
	* has to check the return value against "> count".
	* On exception (or invalid count), returns 0.
	*
	* Unlike strnlen_user, this can be used from IRQ handler etc. because
	* it disables pagefaults.
	*/
	long strnlen_user_nofault(const void __user *unsafe_addr, long count)
	{
	mm_segment_t old_fs;
	int ret;

	old_fs = force_uaccess_begin();
	pagefault_disable();
	ret = strnlen_user(unsafe_addr, count);
	pagefault_enable();
	force_uaccess_end(old_fs);

	return ret;
	}