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authorDavi Arnaut <davi.arnaut@gmail.com>2006-03-24 03:18:42 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-03-24 07:33:31 -0800
commit96840aa00a031069a136ec4c55d0bdd09ac6d3a7 (patch)
treef93592ca47f2412aa0cce3ce4c116d1678a42239 /mm/util.c
parent6687a97d4041f996f725902d2990e5de6ef5cbe5 (diff)
downloadlinux-96840aa00a031069a136ec4c55d0bdd09ac6d3a7.tar.gz
[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: 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>
Diffstat (limited to 'mm/util.c')
-rw-r--r--mm/util.c37
1 files changed, 37 insertions, 0 deletions
diff --git a/mm/util.c b/mm/util.c
index 5f4bb59da63..49e29f751b5 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);