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-rw-r--r--include/linux/string.h1
-rw-r--r--mm/util.c30
2 files changed, 31 insertions, 0 deletions
diff --git a/include/linux/string.h b/include/linux/string.h
index d18fc198aa2..8852739f36d 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -12,6 +12,7 @@
#include <linux/stddef.h> /* for NULL */
extern char *strndup_user(const char __user *, long);
+extern void *memdup_user(const void __user *, size_t);
/*
* Include machine specific inline routines
diff --git a/mm/util.c b/mm/util.c
index 37eaccdf305..7c122e49f76 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -70,6 +70,36 @@ void *kmemdup(const void *src, size_t len, gfp_t gfp)
EXPORT_SYMBOL(kmemdup);
/**
+ * memdup_user - duplicate memory region from user space
+ *
+ * @src: source address in user space
+ * @len: number of bytes to copy
+ *
+ * Returns an ERR_PTR() on failure.
+ */
+void *memdup_user(const void __user *src, size_t len)
+{
+ void *p;
+
+ /*
+ * Always use GFP_KERNEL, since copy_from_user() can sleep and
+ * cause pagefault, which makes it pointless to use GFP_NOFS
+ * or GFP_ATOMIC.
+ */
+ p = kmalloc_track_caller(len, GFP_KERNEL);
+ if (!p)
+ return ERR_PTR(-ENOMEM);
+
+ if (copy_from_user(p, src, len)) {
+ kfree(p);
+ return ERR_PTR(-EFAULT);
+ }
+
+ return p;
+}
+EXPORT_SYMBOL(memdup_user);
+
+/**
* __krealloc - like krealloc() but don't free @p.
* @p: object to reallocate memory for.
* @new_size: how many bytes of memory are required.