Merge tag 'v5.4-rc5' into next

Sync up with mainline.

1 files changed, 23 insertions, 3 deletions

diff --git a/include/linux/string.h b/include/linux/string.h
index 4deb11f7976b..b6ccdc2c7f02 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -227,7 +227,26 @@ static inline bool strstarts(const char *str, const char *prefix)
 }
 
 size_t memweight(const void *ptr, size_t bytes);
-void memzero_explicit(void *s, size_t count);
+
+/**
+ * memzero_explicit - Fill a region of memory (e.g. sensitive
+ *		      keying data) with 0s.
+ * @s: Pointer to the start of the area.
+ * @count: The size of the area.
+ *
+ * Note: usually using memset() is just fine (!), but in cases
+ * where clearing out _local_ data at the end of a scope is
+ * necessary, memzero_explicit() should be used instead in
+ * order to prevent the compiler from optimising away zeroing.
+ *
+ * memzero_explicit() doesn't need an arch-specific version as
+ * it just invokes the one of memset() implicitly.
+ */
+static inline void memzero_explicit(void *s, size_t count)
+{
+	memset(s, 0, count);
+	barrier_data(s);
+}
 
 /**
  * kbasename - return the last part of a pathname.
@@ -474,8 +493,9 @@ static inline void memcpy_and_pad(void *dest, size_t dest_len,
  * But this can lead to bugs due to typos, or if prefix is a pointer
  * and not a constant. Instead use str_has_prefix().
  *
- * Returns: 0 if @str does not start with @prefix
-         strlen(@prefix) if @str does start with @prefix
+ * Returns:
+ * * strlen(@prefix) if @str starts with @prefix
+ * * 0 if @str does not start with @prefix
  */
 static __always_inline size_t str_has_prefix(const char *str, const char *prefix)
 {