From: Daniel Borkmann <daniel@iogearbox.net>
To: "Gustavo A. R. Silva" <gustavoars@kernel.org>,
Kees Cook <keescook@chromium.org>,
linux-kernel@vger.kernel.org
Cc: x86@kernel.org, dm-devel@redhat.com,
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Subject: Re: [PATCH][next] treewide: uapi: Replace zero-length arrays with flexible-array members
Date: Mon, 27 Jun 2022 20:27:37 +0200 [thread overview]
Message-ID: <6bc1e94c-ce1d-a074-7d0c-8dbe6ce22637@iogearbox.net> (raw)
In-Reply-To: <20220627180432.GA136081@embeddedor>
On 6/27/22 8:04 PM, Gustavo A. R. Silva 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@intel.com/
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> ---
> Hi all!
>
> JFYI: I'm adding this to my -next tree. :)
Fyi, this breaks BPF CI:
https://github.com/kernel-patches/bpf/runs/7078719372?check_suite_focus=true
[...]
progs/map_ptr_kern.c:314:26: error: field 'trie_key' with variable sized type 'struct bpf_lpm_trie_key' not at the end of a struct or class is a GNU extension [-Werror,-Wgnu-variable-sized-type-not-at-end]
struct bpf_lpm_trie_key trie_key;
^
1 error generated.
make: *** [Makefile:519: /tmp/runner/work/bpf/bpf/tools/testing/selftests/bpf/map_ptr_kern.o] Error 1
make: *** Waiting for unfinished jobs....
Error: Process completed with exit code 2.
______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/
next prev parent reply other threads:[~2022-06-27 18:28 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-27 18:04 [PATCH][next] treewide: uapi: Replace zero-length arrays with flexible-array members Gustavo A. R. Silva
2022-06-27 18:27 ` Daniel Borkmann [this message]
2022-06-27 18:35 ` Gustavo A. R. Silva
2022-06-28 0:40 ` Jason Gunthorpe
2022-06-28 0:58 ` Gustavo A. R. Silva
2022-06-28 2:21 ` Gustavo A. R. Silva
2022-06-28 13:36 ` Jason Gunthorpe
2022-06-28 13:56 ` Gustavo A. R. Silva
2022-06-28 17:54 ` Kees Cook
2022-06-28 18:44 ` Jason Gunthorpe
2022-06-27 19:53 ` Stephen Hemminger
2022-06-28 14:18 ` Gustavo A. R. Silva
2022-06-27 22:31 ` Dan Williams
2022-06-28 7:27 ` Geert Uytterhoeven
2022-06-28 18:05 ` Kees Cook
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