diff options
| -rw-r--r-- | lib/strnlen_user.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/lib/strnlen_user.c b/lib/strnlen_user.c index 11649615c505..fe9a32591c24 100644 --- a/lib/strnlen_user.c +++ b/lib/strnlen_user.c @@ -90,8 +90,15 @@ static inline long do_strnlen_user(const char __user *src, unsigned long count, * Get the size of a NUL-terminated string in user space. * * Returns the size of the string INCLUDING the terminating NUL. - * If the string is too long, returns 'count+1'. + * 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. + * + * NOTE! You should basically never use this function. There is + * almost never any valid case for using the length of a user space + * string, since the string can be changed at any time by other + * threads. Use "strncpy_from_user()" instead to get a stable copy + * of the string. */ long strnlen_user(const char __user *str, long count) { |