diff options
Diffstat (limited to 'mm/maccess.c')
| -rw-r--r-- | mm/maccess.c | 167 |
1 files changed, 157 insertions, 10 deletions
diff --git a/mm/maccess.c b/mm/maccess.c index 78f9274dd49d..03ea550f5a74 100644 --- a/mm/maccess.c +++ b/mm/maccess.c @@ -5,8 +5,32 @@ #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 location + * 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 @@ -29,17 +53,41 @@ long __probe_kernel_read(void *dst, const void *src, size_t size) mm_segment_t old_fs = get_fs(); set_fs(KERNEL_DS); - pagefault_disable(); - ret = __copy_from_user_inatomic(dst, - (__force const void __user *)src, size); - pagefault_enable(); + ret = probe_read_common(dst, (__force const void __user *)src, size); set_fs(old_fs); - return ret ? -EFAULT : 0; + 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 @@ -48,6 +96,7 @@ EXPORT_SYMBOL_GPL(probe_kernel_read); * 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"))); @@ -57,16 +106,41 @@ long __probe_kernel_write(void *dst, const void *src, size_t size) 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(); + ret = probe_write_common((__force void __user *)dst, src, size); set_fs(old_fs); - return ret ? -EFAULT : 0; + 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. @@ -105,3 +179,76 @@ long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count) 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; +} |