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[PATCH] strndup_user()

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This patch series creates a strndup_user() function to easy copying C strings
from userspace.  Also we avoid common pitfalls like userspace modifying the
final \0 after the strlen_user().

Signed-off-by: Davi Arnaut <davi.arnaut@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Davi Arnaut 2006-03-24 03:18:42 -08:00 • committed by Linus Torvalds
parent 6687a97d40
commit 96840aa00a
2 changed files with 39 additions and 0 deletions
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2
include/linux/string.h
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@ -18,6 +18,8 @@ extern char * strsep(char **,const char *);
extern __kernel_size_t strspn(const char *,const char *); extern __kernel_size_t strspn(const char *,const char *);
extern __kernel_size_t strcspn(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 * Include machine specific inline routines
*/ */

37
mm/util.c
View file

@ -1,6 +1,8 @@
#include <linux/slab.h> #include <linux/slab.h>
#include <linux/string.h> #include <linux/string.h>
#include <linux/module.h> #include <linux/module.h>
#include <linux/err.h>
#include <asm/uaccess.h>
/** /**
* kzalloc - allocate memory. The memory is set to zero. * kzalloc - allocate memory. The memory is set to zero.
@ -37,3 +39,38 @@ char *kstrdup(const char *s, gfp_t gfp)
return buf; return buf;
} }
EXPORT_SYMBOL(kstrdup); 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);