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Commit 96840aa0 authored by Davi Arnaut's avatar Davi Arnaut Committed by Linus Torvalds
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[PATCH] strndup_user() 



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: default avatarDavi Arnaut <davi.arnaut@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 6687a97d

include/linux/string.h

+2 −0
Original line number Original line Diff line number Diff line
@@ -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

 */

 */

mm/util.c

+37 −0
Original line number Original line Diff line number Diff line 
#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);