1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Access kernel memory without faulting.
  4 */
  5#include <linux/export.h>
  6#include <linux/mm.h>
  7#include <linux/uaccess.h>
  8
  9static __always_inline long
 10probe_read_common(void *dst, const void __user *src, size_t size)
 11{
 12	long ret;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 13
 14	pagefault_disable();
 15	ret = __copy_from_user_inatomic(dst, src, size);
 
 
 
 
 
 
 16	pagefault_enable();
 17
 18	return ret ? -EFAULT : 0;
 
 
 19}
 
 20
 21/**
 22 * probe_kernel_read(): safely attempt to read from a kernel-space location
 23 * @dst: pointer to the buffer that shall take the data
 24 * @src: address to read from
 25 * @size: size of the data chunk
 26 *
 27 * Safely read from address @src to the buffer at @dst.  If a kernel fault
 28 * happens, handle that and return -EFAULT.
 29 *
 30 * We ensure that the copy_from_user is executed in atomic context so that
 31 * do_page_fault() doesn't attempt to take mmap_sem.  This makes
 32 * probe_kernel_read() suitable for use within regions where the caller
 33 * already holds mmap_sem, or other locks which nest inside mmap_sem.
 34 */
 35
 36long __weak probe_kernel_read(void *dst, const void *src, size_t size)
 37    __attribute__((alias("__probe_kernel_read")));
 
 38
 39long __probe_kernel_read(void *dst, const void *src, size_t size)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 40{
 41	long ret;
 42	mm_segment_t old_fs = get_fs();
 43
 44	set_fs(KERNEL_DS);
 45	ret = probe_read_common(dst, (__force const void __user *)src, size);
 46	set_fs(old_fs);
 
 47
 48	return ret;
 
 
 
 
 
 
 
 
 
 
 
 
 
 49}
 50EXPORT_SYMBOL_GPL(probe_kernel_read);
 51
 52/**
 53 * probe_user_read(): safely attempt to read from a user-space location
 54 * @dst: pointer to the buffer that shall take the data
 55 * @src: address to read from. This must be a user address.
 56 * @size: size of the data chunk
 57 *
 58 * Safely read from user address @src to the buffer at @dst. If a kernel fault
 59 * happens, handle that and return -EFAULT.
 60 */
 61
 62long __weak probe_user_read(void *dst, const void __user *src, size_t size)
 63    __attribute__((alias("__probe_user_read")));
 64
 65long __probe_user_read(void *dst, const void __user *src, size_t size)
 66{
 67	long ret = -EFAULT;
 68	mm_segment_t old_fs = get_fs();
 69
 70	set_fs(USER_DS);
 71	if (access_ok(src, size))
 72		ret = probe_read_common(dst, src, size);
 73	set_fs(old_fs);
 74
 75	return ret;
 
 
 76}
 77EXPORT_SYMBOL_GPL(probe_user_read);
 78
 79/**
 80 * probe_kernel_write(): safely attempt to write to a location
 81 * @dst: address to write to
 82 * @src: pointer to the data that shall be written
 83 * @size: size of the data chunk
 84 *
 85 * Safely write to address @dst from the buffer at @src.  If a kernel fault
 86 * happens, handle that and return -EFAULT.
 87 */
 88long __weak probe_kernel_write(void *dst, const void *src, size_t size)
 89    __attribute__((alias("__probe_kernel_write")));
 90
 91long __probe_kernel_write(void *dst, const void *src, size_t size)
 92{
 93	long ret;
 94	mm_segment_t old_fs = get_fs();
 95
 96	set_fs(KERNEL_DS);
 97	pagefault_disable();
 98	ret = __copy_to_user_inatomic((__force void __user *)dst, src, size);
 99	pagefault_enable();
100	set_fs(old_fs);
101
102	return ret ? -EFAULT : 0;
103}
104EXPORT_SYMBOL_GPL(probe_kernel_write);
105
106
107/**
108 * strncpy_from_unsafe: - Copy a NUL terminated string from unsafe address.
109 * @dst:   Destination address, in kernel space.  This buffer must be at
110 *         least @count bytes long.
111 * @unsafe_addr: Unsafe address.
112 * @count: Maximum number of bytes to copy, including the trailing NUL.
113 *
114 * Copies a NUL-terminated string from unsafe address to kernel buffer.
115 *
116 * On success, returns the length of the string INCLUDING the trailing NUL.
117 *
118 * If access fails, returns -EFAULT (some data may have been copied
119 * and the trailing NUL added).
120 *
121 * If @count is smaller than the length of the string, copies @count-1 bytes,
122 * sets the last byte of @dst buffer to NUL and returns @count.
123 */
124long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count)
125{
126	mm_segment_t old_fs = get_fs();
127	const void *src = unsafe_addr;
128	long ret;
129
130	if (unlikely(count <= 0))
131		return 0;
132
133	set_fs(KERNEL_DS);
134	pagefault_disable();
135
136	do {
137		ret = __get_user(*dst++, (const char __user __force *)src++);
138	} while (dst[-1] && ret == 0 && src - unsafe_addr < count);
139
140	dst[-1] = '\0';
141	pagefault_enable();
142	set_fs(old_fs);
 
 
143
144	return ret ? -EFAULT : src - unsafe_addr;
 
 
145}
 
146
147/**
148 * strncpy_from_unsafe_user: - Copy a NUL terminated string from unsafe user
149 *				address.
150 * @dst:   Destination address, in kernel space.  This buffer must be at
151 *         least @count bytes long.
152 * @unsafe_addr: Unsafe user address.
153 * @count: Maximum number of bytes to copy, including the trailing NUL.
154 *
155 * Copies a NUL-terminated string from unsafe user address to kernel buffer.
156 *
157 * On success, returns the length of the string INCLUDING the trailing NUL.
158 *
159 * If access fails, returns -EFAULT (some data may have been copied
160 * and the trailing NUL added).
161 *
162 * If @count is smaller than the length of the string, copies @count-1 bytes,
163 * sets the last byte of @dst buffer to NUL and returns @count.
164 */
165long strncpy_from_unsafe_user(char *dst, const void __user *unsafe_addr,
166			      long count)
167{
168	mm_segment_t old_fs = get_fs();
169	long ret;
170
171	if (unlikely(count <= 0))
172		return 0;
173
174	set_fs(USER_DS);
175	pagefault_disable();
176	ret = strncpy_from_user(dst, unsafe_addr, count);
177	pagefault_enable();
178	set_fs(old_fs);
179
180	if (ret >= count) {
181		ret = count;
182		dst[ret - 1] = '\0';
183	} else if (ret > 0) {
184		ret++;
185	}
186
187	return ret;
188}
189
190/**
191 * strnlen_unsafe_user: - Get the size of a user string INCLUDING final NUL.
192 * @unsafe_addr: The string to measure.
193 * @count: Maximum count (including NUL)
194 *
195 * Get the size of a NUL-terminated string in user space without pagefault.
196 *
197 * Returns the size of the string INCLUDING the terminating NUL.
198 *
199 * If the string is too long, returns a number larger than @count. User
200 * has to check the return value against "> count".
201 * On exception (or invalid count), returns 0.
202 *
203 * Unlike strnlen_user, this can be used from IRQ handler etc. because
204 * it disables pagefaults.
205 */
206long strnlen_unsafe_user(const void __user *unsafe_addr, long count)
207{
208	mm_segment_t old_fs = get_fs();
209	int ret;
210
211	set_fs(USER_DS);
212	pagefault_disable();
213	ret = strnlen_user(unsafe_addr, count);
214	pagefault_enable();
215	set_fs(old_fs);
216
217	return ret;
218}

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Access kernel or user memory without faulting.
  4 */
  5#include <linux/export.h>
  6#include <linux/mm.h>
  7#include <linux/uaccess.h>
  8
  9bool __weak copy_from_kernel_nofault_allowed(const void *unsafe_src,
 10		size_t size)
 11{
 12	return true;
 13}
 14
 15#define copy_from_kernel_nofault_loop(dst, src, len, type, err_label)	\
 16	while (len >= sizeof(type)) {					\
 17		__get_kernel_nofault(dst, src, type, err_label);		\
 18		dst += sizeof(type);					\
 19		src += sizeof(type);					\
 20		len -= sizeof(type);					\
 21	}
 22
 23long copy_from_kernel_nofault(void *dst, const void *src, size_t size)
 24{
 25	unsigned long align = 0;
 26
 27	if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
 28		align = (unsigned long)dst | (unsigned long)src;
 29
 30	if (!copy_from_kernel_nofault_allowed(src, size))
 31		return -ERANGE;
 32
 33	pagefault_disable();
 34	if (!(align & 7))
 35		copy_from_kernel_nofault_loop(dst, src, size, u64, Efault);
 36	if (!(align & 3))
 37		copy_from_kernel_nofault_loop(dst, src, size, u32, Efault);
 38	if (!(align & 1))
 39		copy_from_kernel_nofault_loop(dst, src, size, u16, Efault);
 40	copy_from_kernel_nofault_loop(dst, src, size, u8, Efault);
 41	pagefault_enable();
 42	return 0;
 43Efault:
 44	pagefault_enable();
 45	return -EFAULT;
 46}
 47EXPORT_SYMBOL_GPL(copy_from_kernel_nofault);
 48
 49#define copy_to_kernel_nofault_loop(dst, src, len, type, err_label)	\
 50	while (len >= sizeof(type)) {					\
 51		__put_kernel_nofault(dst, src, type, err_label);		\
 52		dst += sizeof(type);					\
 53		src += sizeof(type);					\
 54		len -= sizeof(type);					\
 55	}
 
 
 
 
 
 
 
 56
 57long copy_to_kernel_nofault(void *dst, const void *src, size_t size)
 58{
 59	unsigned long align = 0;
 60
 61	if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
 62		align = (unsigned long)dst | (unsigned long)src;
 63
 64	pagefault_disable();
 65	if (!(align & 7))
 66		copy_to_kernel_nofault_loop(dst, src, size, u64, Efault);
 67	if (!(align & 3))
 68		copy_to_kernel_nofault_loop(dst, src, size, u32, Efault);
 69	if (!(align & 1))
 70		copy_to_kernel_nofault_loop(dst, src, size, u16, Efault);
 71	copy_to_kernel_nofault_loop(dst, src, size, u8, Efault);
 72	pagefault_enable();
 73	return 0;
 74Efault:
 75	pagefault_enable();
 76	return -EFAULT;
 77}
 78
 79long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count)
 80{
 81	const void *src = unsafe_addr;
 
 82
 83	if (unlikely(count <= 0))
 84		return 0;
 85	if (!copy_from_kernel_nofault_allowed(unsafe_addr, count))
 86		return -ERANGE;
 87
 88	pagefault_disable();
 89	do {
 90		__get_kernel_nofault(dst, src, u8, Efault);
 91		dst++;
 92		src++;
 93	} while (dst[-1] && src - unsafe_addr < count);
 94	pagefault_enable();
 95
 96	dst[-1] = '\0';
 97	return src - unsafe_addr;
 98Efault:
 99	pagefault_enable();
100	dst[0] = '\0';
101	return -EFAULT;
102}
 
103
104/**
105 * copy_from_user_nofault(): safely attempt to read from a user-space location
106 * @dst: pointer to the buffer that shall take the data
107 * @src: address to read from. This must be a user address.
108 * @size: size of the data chunk
109 *
110 * Safely read from user address @src to the buffer at @dst. If a kernel fault
111 * happens, handle that and return -EFAULT.
112 */
113long copy_from_user_nofault(void *dst, const void __user *src, size_t size)
 
 
 
 
114{
115	long ret = -EFAULT;
116	if (access_ok(src, size)) {
117		pagefault_disable();
118		ret = __copy_from_user_inatomic(dst, src, size);
119		pagefault_enable();
120	}
 
121
122	if (ret)
123		return -EFAULT;
124	return 0;
125}
126EXPORT_SYMBOL_GPL(copy_from_user_nofault);
127
128/**
129 * copy_to_user_nofault(): safely attempt to write to a user-space location
130 * @dst: address to write to
131 * @src: pointer to the data that shall be written
132 * @size: size of the data chunk
133 *
134 * Safely write to address @dst from the buffer at @src.  If a kernel fault
135 * happens, handle that and return -EFAULT.
136 */
137long copy_to_user_nofault(void __user *dst, const void *src, size_t size)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
138{
139	long ret = -EFAULT;
 
 
 
 
 
 
 
 
 
 
 
 
140
141	if (access_ok(dst, size)) {
142		pagefault_disable();
143		ret = __copy_to_user_inatomic(dst, src, size);
144		pagefault_enable();
145	}
146
147	if (ret)
148		return -EFAULT;
149	return 0;
150}
151EXPORT_SYMBOL_GPL(copy_to_user_nofault);
152
153/**
154 * strncpy_from_user_nofault: - Copy a NUL terminated string from unsafe user
155 *				address.
156 * @dst:   Destination address, in kernel space.  This buffer must be at
157 *         least @count bytes long.
158 * @unsafe_addr: Unsafe user address.
159 * @count: Maximum number of bytes to copy, including the trailing NUL.
160 *
161 * Copies a NUL-terminated string from unsafe user address to kernel buffer.
162 *
163 * On success, returns the length of the string INCLUDING the trailing NUL.
164 *
165 * If access fails, returns -EFAULT (some data may have been copied
166 * and the trailing NUL added).
167 *
168 * If @count is smaller than the length of the string, copies @count-1 bytes,
169 * sets the last byte of @dst buffer to NUL and returns @count.
170 */
171long strncpy_from_user_nofault(char *dst, const void __user *unsafe_addr,
172			      long count)
173{
 
174	long ret;
175
176	if (unlikely(count <= 0))
177		return 0;
178
 
179	pagefault_disable();
180	ret = strncpy_from_user(dst, unsafe_addr, count);
181	pagefault_enable();
 
182
183	if (ret >= count) {
184		ret = count;
185		dst[ret - 1] = '\0';
186	} else if (ret > 0) {
187		ret++;
188	}
189
190	return ret;
191}
192
193/**
194 * strnlen_user_nofault: - Get the size of a user string INCLUDING final NUL.
195 * @unsafe_addr: The string to measure.
196 * @count: Maximum count (including NUL)
197 *
198 * Get the size of a NUL-terminated string in user space without pagefault.
199 *
200 * Returns the size of the string INCLUDING the terminating NUL.
201 *
202 * If the string is too long, returns a number larger than @count. User
203 * has to check the return value against "> count".
204 * On exception (or invalid count), returns 0.
205 *
206 * Unlike strnlen_user, this can be used from IRQ handler etc. because
207 * it disables pagefaults.
208 */
209long strnlen_user_nofault(const void __user *unsafe_addr, long count)
210{
 
211	int ret;
212
 
213	pagefault_disable();
214	ret = strnlen_user(unsafe_addr, count);
215	pagefault_enable();
 
216
217	return ret;
218}
219
220void __copy_overflow(int size, unsigned long count)
221{
222	WARN(1, "Buffer overflow detected (%d < %lu)!\n", size, count);
223}
224EXPORT_SYMBOL(__copy_overflow);