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-rw-r--r--mm/maccess.c321
1 files changed, 321 insertions, 0 deletions
diff --git a/mm/maccess.c b/mm/maccess.c
new file mode 100644
index 000000000..f6ea117a6
--- /dev/null
+++ b/mm/maccess.c
@@ -0,0 +1,321 @@
+// 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)
+{
+ if (!copy_from_kernel_nofault_allowed(src, size))
+ return -ERANGE;
+
+ pagefault_disable();
+ copy_from_kernel_nofault_loop(dst, src, size, u64, Efault);
+ copy_from_kernel_nofault_loop(dst, src, size, u32, Efault);
+ 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)
+{
+ pagefault_disable();
+ copy_to_kernel_nofault_loop(dst, src, size, u64, Efault);
+ copy_to_kernel_nofault_loop(dst, src, size, u32, Efault);
+ 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;
+}