usb: gadget: f_fs: Annotate struct ffs_buffer with __counted_by

Prepare for the coming implementation by GCC and Clang of the __counted_by attribute. Flexible array members annotated with __counted_by can have their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family functions).

As found with Coccinelle[1], add __counted_by for struct ffs_buffer.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc Greg Kroah-Hartman <[email protected]>

Cc John Keeping <[email protected]>

Cc Udipto Goswami <[email protected]>

Cc Linyu Yuan <[email protected]>

Cc [email protected]

Signed-off-by Kees Cook <[email protected]>

---
  drivers/usb/gadget/function/f_fs.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

drivers/usb/gadget/function/f_fs.c +1 -1

index 6e9ef35a43a7..af400d083777 100644
@@ -202,7 +202,7 @@ struct ffs_epfile {
  struct ffs_buffer {
  	size_t length;
  	char *data;
-	char storage[];
+	char storage[] __counted_by(length);
  };
 
  /*  ffs_io_data structure ***************************************************/

Prepare for the coming implementation by GCC and Clang of the __counted_by attribute. Flexible array members annotated with __counted_by can have their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family functions).

As found with Coccinelle[1], add __counted_by for struct ffs_buffer.

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