// 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; } #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[-1] = '\0'; return -EFAULT; } /** * 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; if (access_ok(src, size)) { pagefault_disable(); ret = __copy_from_user_inatomic(dst, src, size); pagefault_enable(); } 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; if (access_ok(dst, size)) { pagefault_disable(); ret = __copy_to_user_inatomic(dst, src, size); pagefault_enable(); } 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) { long ret; if (unlikely(count <= 0)) return 0; pagefault_disable(); ret = strncpy_from_user(dst, unsafe_addr, count); pagefault_enable(); 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) { int ret; pagefault_disable(); ret = strnlen_user(unsafe_addr, count); pagefault_enable(); return ret; } void __copy_overflow(int size, unsigned long count) { WARN(1, "Buffer overflow detected (%d < %lu)!\n", size, count); } EXPORT_SYMBOL(__copy_overflow);