fs: Fix filename init after recent refactoring

getname_flags() should save __user pointer "filename" in filename->uptr.
However, this logic is broken by a recent refactoring. Fix it by passing
__user pointer filename to helper initname().

Fixes: 6118510 ("fs: dedup handling of struct filename init and refcounts bumps")
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Christian Brauner <brauner@kernel.org>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/20250409220534.3635801-1-song@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: liu-song-6

fs/namei.c

@@ -125,9 +125,9 @@
 
 #define EMBEDDED_NAME_MAX	(PATH_MAX - offsetof(struct filename, iname))
 
-static inline void initname(struct filename *name)
+static inline void initname(struct filename *name, const char __user *uptr)
 {
-	name->uptr = NULL;
+	name->uptr = uptr;
 	name->aname = NULL;
 	atomic_set(&name->refcnt, 1);
 }
@@ -210,7 +210,7 @@ getname_flags(const char __user *filename, int flags)
 			return ERR_PTR(-ENAMETOOLONG);
 		}
 	}
-	initname(result);
+	initname(result, filename);
 	audit_getname(result);
 	return result;
 }
@@ -268,7 +268,7 @@ struct filename *getname_kernel(const char * filename)
 		return ERR_PTR(-ENAMETOOLONG);
 	}
 	memcpy((char *)result->name, filename, len);
-	initname(result);
+	initname(result, NULL);
 	audit_getname(result);
 	return result;
 }