On Mon, 27 Jun 2022 20:04:32 +0200
"Gustavo A. R. Silva" <gustavoars@xxxxxxxxxx> wrote:
> 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].
>
> This code was transformed with the help of Coccinelle:
> (linux-5.19-rc2$ spatch --jobs $(getconf _NPROCESSORS_ONLN) --sp-file script.cocci --include-headers --dir . > output.patch)
>
> @@
> identifier S, member, array;
> type T1, T2;
> @@
>
> struct S {
> ...
> T1 member;
> T2 array[
> - 0
> ];
> };
>
> -fstrict-flex-arrays=3 is coming and we need to land these changes
> to prevent issues like these in the short future:
>
> ../fs/minix/dir.c:337:3: warning: 'strcpy' will always overflow; destination buffer has size 0,
> but the source string has length 2 (including NUL byte) [-Wfortify-source]
> strcpy(de3->name, ".");
> ^
>
> Since these are all [0] to [] changes, the risk to UAPI is nearly zero. If
> this breaks anything, we can use a union with a new member name.
>
> [1] https://en.wikipedia.org/wiki/Flexible_array_member
> [2] https://www.kernel.org/doc/html/v5.16/process/deprecated.html#zero-length-and-one-element-arrays
>
> Link: https://github.com/KSPP/linux/issues/78
> Build-tested-by: https://lore.kernel.org/lkml/62b675ec.wKX6AOZ6cbE71vtF%25lkp@xxxxxxxxx/
> Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
Thanks this fixes warning with gcc-12 in iproute2.
In function ‘xfrm_algo_parse’,
inlined from ‘xfrm_state_modify.constprop’ at xfrm_state.c:573:5:
xfrm_state.c:162:32: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]
162 | buf[j] = val;
| ~~~~~~~^~~~~
