Commit c72a8268 authored Aug 10, 2021 by Gustavo A. R. Silva Committed by Anna Schumaker Jan 06, 2022

nfs41: pnfs: filelayout: Replace one-element array with flexible-array member

There is a regular need in the kernel to provide a way to declare having
a dynamically sized set of trailing elements in a structure. Kernel code
should always use “flexible array members”[1] for these cases. The older
style of one-element or zero-length arrays should no longer be used[2].

Refactor the code a bit according to the use of a flexible-array member
in struct nfs4_file_layout_dsaddr instead of a one-element array, and
use the struct_size() helper.

This helps with the ongoing efforts to globally enable -Warray-bounds
and get us closer to being able to tighten the FORTIFY_SOURCE routines
on memcpy().

This issue was found with the help of Coccinelle and audited and fixed,
manually.

[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.10/process/deprecated.html#zero-length-and-one-element-arrays

Link: https://github.com/KSPP/linux/issues/79
Link: https://github.com/KSPP/linux/issues/109


Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

parent 4b0c359b

fs/nfs/filelayout/filelayout.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -51,7 +51,7 @@ struct nfs4_file_layout_dsaddr {
		u32 stripe_count;
		u8 *stripe_indices;
		u32 ds_num;
		struct nfs4_pnfs_ds *ds_list[1];
		struct nfs4_pnfs_ds *ds_list[];
		};

		struct nfs4_filelayout_segment {

fs/nfs/filelayout/filelayoutdev.c

+1 −3

Original line number	Diff line number	Diff line
		@@ -136,9 +136,7 @@ nfs4_fl_alloc_deviceid_node(struct nfs_server server, struct pnfs_device pdev,
		goto out_err_free_stripe_indices;
		}

		dsaddr = kzalloc(sizeof(*dsaddr) +
		(sizeof(struct nfs4_pnfs_ds ) (num - 1)),
		gfp_flags);
		dsaddr = kzalloc(struct_size(dsaddr, ds_list, num), gfp_flags);
		if (!dsaddr)
		goto out_err_free_stripe_indices;