diff options
| -rw-r--r-- | include/linux/string.h | 2 | ||||
| -rw-r--r-- | mm/util.c | 37 |
2 files changed, 39 insertions, 0 deletions
diff --git a/include/linux/string.h b/include/linux/string.h index 369be3264a55..dee221429ad0 100644 --- a/include/linux/string.h +++ b/include/linux/string.h @@ -18,6 +18,8 @@ extern char * strsep(char **,const char *); extern __kernel_size_t strspn(const char *,const char *); extern __kernel_size_t strcspn(const char *,const char *); +extern char *strndup_user(const char __user *, long); + /* * Include machine specific inline routines */ diff --git a/mm/util.c b/mm/util.c index 5f4bb59da63c..49e29f751b50 100644 --- a/mm/util.c +++ b/mm/util.c @@ -1,6 +1,8 @@ #include <linux/slab.h> #include <linux/string.h> #include <linux/module.h> +#include <linux/err.h> +#include <asm/uaccess.h> /** * kzalloc - allocate memory. The memory is set to zero. @@ -37,3 +39,38 @@ char *kstrdup(const char *s, gfp_t gfp) return buf; } EXPORT_SYMBOL(kstrdup); + +/* + * strndup_user - duplicate an existing string from user space + * + * @s: The string to duplicate + * @n: Maximum number of bytes to copy, including the trailing NUL. + */ +char *strndup_user(const char __user *s, long n) +{ + char *p; + long length; + + length = strnlen_user(s, n); + + if (!length) + return ERR_PTR(-EFAULT); + + if (length > n) + return ERR_PTR(-EINVAL); + + p = kmalloc(length, GFP_KERNEL); + + if (!p) + return ERR_PTR(-ENOMEM); + + if (copy_from_user(p, s, length)) { + kfree(p); + return ERR_PTR(-EFAULT); + } + + p[length - 1] = '\0'; + + return p; +} +EXPORT_SYMBOL(strndup_user); |