2022-11-18 04:56:34

by Kees Cook

[permalink] [raw]
Subject: [PATCH] ipv4/fib: Replace zero-length array with DECLARE_FLEX_ARRAY() helper

Zero-length arrays are deprecated[1] and are being replaced with
flexible array members in support of the ongoing efforts to tighten the
FORTIFY_SOURCE routines on memcpy(), correctly instrument array indexing
with UBSAN_BOUNDS, and to globally enable -fstrict-flex-arrays=3.

Replace zero-length array with flexible-array member in struct key_vector.

This results in no differences in binary output.

[1] https://github.com/KSPP/linux/issues/78

Cc: Jakub Kicinski <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Hideaki YOSHIFUJI <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Eric Dumazet <[email protected]>
Cc: Paolo Abeni <[email protected]>
Cc: "Gustavo A. R. Silva" <[email protected]>
Cc: [email protected]
Signed-off-by: Kees Cook <[email protected]>
---
net/ipv4/fib_trie.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index 452ff177e4da..c88bf856c443 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -126,7 +126,7 @@ struct key_vector {
/* This list pointer if valid if (pos | bits) == 0 (LEAF) */
struct hlist_head leaf;
/* This array is valid if (pos | bits) > 0 (TNODE) */
- struct key_vector __rcu *tnode[0];
+ DECLARE_FLEX_ARRAY(struct key_vector __rcu *, tnode);
};
};

--
2.34.1



2022-11-18 05:12:50

by Gustavo A. R. Silva

[permalink] [raw]
Subject: Re: [PATCH] ipv4/fib: Replace zero-length array with DECLARE_FLEX_ARRAY() helper

On Thu, Nov 17, 2022 at 08:21:52PM -0800, Kees Cook wrote:
> Zero-length arrays are deprecated[1] and are being replaced with
> flexible array members in support of the ongoing efforts to tighten the
> FORTIFY_SOURCE routines on memcpy(), correctly instrument array indexing
> with UBSAN_BOUNDS, and to globally enable -fstrict-flex-arrays=3.
>
> Replace zero-length array with flexible-array member in struct key_vector.
>
> This results in no differences in binary output.
>
> [1] https://github.com/KSPP/linux/issues/78
>
> Cc: Jakub Kicinski <[email protected]>
> Cc: "David S. Miller" <[email protected]>
> Cc: Hideaki YOSHIFUJI <[email protected]>
> Cc: David Ahern <[email protected]>
> Cc: Eric Dumazet <[email protected]>
> Cc: Paolo Abeni <[email protected]>
> Cc: "Gustavo A. R. Silva" <[email protected]>
> Cc: [email protected]
> Signed-off-by: Kees Cook <[email protected]>

Reviewed-by: Gustavo A. R. Silva <[email protected]>

Thanks!
--
Gustavo

> ---
> net/ipv4/fib_trie.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
> index 452ff177e4da..c88bf856c443 100644
> --- a/net/ipv4/fib_trie.c
> +++ b/net/ipv4/fib_trie.c
> @@ -126,7 +126,7 @@ struct key_vector {
> /* This list pointer if valid if (pos | bits) == 0 (LEAF) */
> struct hlist_head leaf;
> /* This array is valid if (pos | bits) > 0 (TNODE) */
> - struct key_vector __rcu *tnode[0];
> + DECLARE_FLEX_ARRAY(struct key_vector __rcu *, tnode);
> };
> };
>
> --
> 2.34.1
>

2022-11-18 16:01:54

by David Ahern

[permalink] [raw]
Subject: Re: [PATCH] ipv4/fib: Replace zero-length array with DECLARE_FLEX_ARRAY() helper

On 11/17/22 9:21 PM, Kees Cook wrote:
> Zero-length arrays are deprecated[1] and are being replaced with
> flexible array members in support of the ongoing efforts to tighten the
> FORTIFY_SOURCE routines on memcpy(), correctly instrument array indexing
> with UBSAN_BOUNDS, and to globally enable -fstrict-flex-arrays=3.
>
> Replace zero-length array with flexible-array member in struct key_vector.
>
> This results in no differences in binary output.
>
> [1] https://github.com/KSPP/linux/issues/78
>
> Cc: Jakub Kicinski <[email protected]>
> Cc: "David S. Miller" <[email protected]>
> Cc: Hideaki YOSHIFUJI <[email protected]>
> Cc: David Ahern <[email protected]>
> Cc: Eric Dumazet <[email protected]>
> Cc: Paolo Abeni <[email protected]>
> Cc: "Gustavo A. R. Silva" <[email protected]>
> Cc: [email protected]
> Signed-off-by: Kees Cook <[email protected]>
> ---
> net/ipv4/fib_trie.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>

Reviewed-by: David Ahern <[email protected]>


2022-11-21 13:42:18

by patchwork-bot+netdevbpf

[permalink] [raw]
Subject: Re: [PATCH] ipv4/fib: Replace zero-length array with DECLARE_FLEX_ARRAY() helper

Hello:

This patch was applied to netdev/net.git (master)
by David S. Miller <[email protected]>:

On Thu, 17 Nov 2022 20:21:52 -0800 you wrote:
> Zero-length arrays are deprecated[1] and are being replaced with
> flexible array members in support of the ongoing efforts to tighten the
> FORTIFY_SOURCE routines on memcpy(), correctly instrument array indexing
> with UBSAN_BOUNDS, and to globally enable -fstrict-flex-arrays=3.
>
> Replace zero-length array with flexible-array member in struct key_vector.
>
> [...]

Here is the summary with links:
- ipv4/fib: Replace zero-length array with DECLARE_FLEX_ARRAY() helper
https://git.kernel.org/netdev/net/c/764f8485890d

You are awesome, thank you!
--
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