Previously the strndup_user allocation was being done through memdup_user,
and the caller was wrongly traced as being strndup_user
(the correct trace must report the caller of strndup_user).

This is a common problem: in order to get accurate callsite tracing,
a utils function can't allocate through another utils function,
but instead do the allocation himself (or inlined).

Here we fix this by creating an always inlined dup_user() function to
performed the real allocation and to be used by memdup_user and strndup_user.

Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Ezequiel Garcia <redacted>
---
 mm/util.c |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/mm/util.c b/mm/util.c
index dc3036c..48d3ff8b 100644
--- a/mm/util.c
+++ b/mm/util.c

@@ -76,14 +76,14 @@ void *kmemdup(const void *src, size_t len, gfp_t gfp)
 EXPORT_SYMBOL(kmemdup);

 /**
- * memdup_user - duplicate memory region from user space
+ * dup_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)
+static __always_inline void *dup_user(const void __user *src, size_t len)
 {
        void *p;

@@ -103,6 +103,11 @@ void *memdup_user(const void __user *src, size_t len)

        return p;
 }
+
+void *memdup_user(const void __user *src, size_t len)
+{
+       return dup_user(src, len);
+}
 EXPORT_SYMBOL(memdup_user);

 static __always_inline void *__do_krealloc(const void *p, size_t new_size,

@@ -214,7 +219,7 @@ char *strndup_user(const char __user *s, long n)
        if (length > n)
                return ERR_PTR(-EINVAL);

-       p = memdup_user(s, length);
+       p = dup_user(s, length);

        if (IS_ERR(p))
                return p;