debugfs: make sure we can remove u32_array files cleanly

debugfs_create_u32_array() allocates a small structure to wrap
the data and size information about the array. If users ever
try to remove the file this leads to a leak since nothing ever
frees this wrapper.

That said there are no upstream users of debugfs_create_u32_array()
that'd remove a u32 array file (we only have one u32 array user in
CMA), so there is no real bug here.

Make callers pass a wrapper they allocated. This way the lifetime
management of the wrapper is on the caller, and we can avoid the
potential leak in debugfs.

CC: Chucheng Luo <luochucheng@vivo.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 4 deletions

diff --git a/Documentation/filesystems/debugfs.rst b/Documentation/filesystems/debugfs.rst
index 1da7a4b7383d..728ab57a611a 100644
--- a/Documentation/filesystems/debugfs.rst
+++ b/Documentation/filesystems/debugfs.rst
@@ -185,13 +185,17 @@ byte offsets over a base for the register block.
 
 If you want to dump an u32 array in debugfs, you can create file with::
 
+    struct debugfs_u32_array {
+	u32 *array;
+	u32 n_elements;
+    };
+
     void debugfs_create_u32_array(const char *name, umode_t mode,
 			struct dentry *parent,
-			u32 *array, u32 elements);
+			struct debugfs_u32_array *array);
 
-The "array" argument provides data, and the "elements" argument is
-the number of elements in the array. Note: Once array is created its
-size can not be changed.
+The "array" argument wraps a pointer to the array's data and the number
+of its elements. Note: Once array is created its size can not be changed.
 
 There is a helper function to create device related seq_file::