| /* |
| * Access kernel memory without faulting. |
| */ |
| #include <linux/export.h> |
| #include <linux/mm.h> |
| #include <linux/uaccess.h> |
| |
| static __always_inline long |
| probe_read_common(void *dst, const void __user *src, size_t size) |
| { |
| long ret; |
| |
| pagefault_disable(); |
| ret = __copy_from_user_inatomic(dst, src, size); |
| pagefault_enable(); |
| |
| return ret ? -EFAULT : 0; |
| } |
| |
| static __always_inline long |
| probe_write_common(void __user *dst, const void *src, size_t size) |
| { |
| long ret; |
| |
| pagefault_disable(); |
| ret = __copy_to_user_inatomic(dst, src, size); |
| pagefault_enable(); |
| |
| return ret ? -EFAULT : 0; |
| } |
| |
| /** |
| * probe_kernel_read(): safely attempt to read from a kernel-space location |
| * @dst: pointer to the buffer that shall take the data |
| * @src: address to read from |
| * @size: size of the data chunk |
| * |
| * Safely read from address @src to the buffer at @dst. If a kernel fault |
| * happens, handle that and return -EFAULT. |
| * |
| * We ensure that the copy_from_user is executed in atomic context so that |
| * do_page_fault() doesn't attempt to take mmap_sem. This makes |
| * probe_kernel_read() suitable for use within regions where the caller |
| * already holds mmap_sem, or other locks which nest inside mmap_sem. |
| */ |
| |
| long __weak probe_kernel_read(void *dst, const void *src, size_t size) |
| __attribute__((alias("__probe_kernel_read"))); |
| |
| long __probe_kernel_read(void *dst, const void *src, size_t size) |
| { |
| long ret; |
| mm_segment_t old_fs = get_fs(); |
| |
| set_fs(KERNEL_DS); |
| ret = probe_read_common(dst, (__force const void __user *)src, size); |
| set_fs(old_fs); |
| |
| return ret; |
| } |
| EXPORT_SYMBOL_GPL(probe_kernel_read); |
| |
| /** |
| * probe_user_read(): 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 __weak probe_user_read(void *dst, const void __user *src, size_t size) |
| __attribute__((alias("__probe_user_read"))); |
| |
| long __probe_user_read(void *dst, const void __user *src, size_t size) |
| { |
| long ret = -EFAULT; |
| mm_segment_t old_fs = get_fs(); |
| |
| set_fs(USER_DS); |
| if (access_ok(VERIFY_READ, src, size)) |
| ret = probe_read_common(dst, src, size); |
| set_fs(old_fs); |
| |
| return ret; |
| } |
| EXPORT_SYMBOL_GPL(probe_user_read); |
| |
| /** |
| * probe_kernel_write(): 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 __weak probe_kernel_write(void *dst, const void *src, size_t size) |
| __attribute__((alias("__probe_kernel_write"))); |
| |
| long __probe_kernel_write(void *dst, const void *src, size_t size) |
| { |
| long ret; |
| mm_segment_t old_fs = get_fs(); |
| |
| set_fs(KERNEL_DS); |
| ret = probe_write_common((__force void __user *)dst, src, size); |
| set_fs(old_fs); |
| |
| return ret; |
| } |
| EXPORT_SYMBOL_GPL(probe_kernel_write); |
| |
| /** |
| * probe_user_write(): 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 __weak probe_user_write(void __user *dst, const void *src, size_t size) |
| __attribute__((alias("__probe_user_write"))); |
| |
| long __probe_user_write(void __user *dst, const void *src, size_t size) |
| { |
| long ret = -EFAULT; |
| mm_segment_t old_fs = get_fs(); |
| |
| set_fs(USER_DS); |
| if (access_ok(VERIFY_WRITE, dst, size)) |
| ret = probe_write_common(dst, src, size); |
| set_fs(old_fs); |
| |
| return ret; |
| } |
| EXPORT_SYMBOL_GPL(probe_user_write); |
| |
| /** |
| * strncpy_from_unsafe: - 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 @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_unsafe(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; |
| |
| 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; |
| } |
| |
| /** |
| * strncpy_from_unsafe_user: - 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_unsafe_user(char *dst, const void __user *unsafe_addr, |
| long count) |
| { |
| mm_segment_t old_fs = get_fs(); |
| long ret; |
| |
| if (unlikely(count <= 0)) |
| return 0; |
| |
| set_fs(USER_DS); |
| pagefault_disable(); |
| ret = strncpy_from_user(dst, unsafe_addr, count); |
| pagefault_enable(); |
| set_fs(old_fs); |
| |
| if (ret >= count) { |
| ret = count; |
| dst[ret - 1] = '\0'; |
| } else if (ret > 0) { |
| ret++; |
| } |
| |
| return ret; |
| } |
| |
| /** |
| * strnlen_unsafe_user: - 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_unsafe_user(const void __user *unsafe_addr, long count) |
| { |
| mm_segment_t old_fs = get_fs(); |
| int ret; |
| |
| set_fs(USER_DS); |
| pagefault_disable(); |
| ret = strnlen_user(unsafe_addr, count); |
| pagefault_enable(); |
| set_fs(old_fs); |
| |
| return ret; |
| } |