linux-kernel - Re: [PATCH 2/4] tools: ynl: zero-initialize struct ynl

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Message-ID: <20251020161639.7b1734c6@kernel.org>
Date: Mon, 20 Oct 2025 16:16:39 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Zahari Doychev <zahari.doychev@...ux.com>
Cc: donald.hunter@...il.com, davem@...emloft.net, edumazet@...gle.com,
 pabeni@...hat.com, horms@...nel.org, jacob.e.keller@...el.com,
 ast@...erby.net, matttbe@...nel.org, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, jhs@...atatu.com, xiyou.wangcong@...il.com,
 jiri@...nulli.us, johannes@...solutions.net
Subject: Re: [PATCH 2/4] tools: ynl: zero-initialize struct ynl_sock memory

On Sat, 18 Oct 2025 17:17:35 +0200 Zahari Doychev wrote:
> The memory belonging to tx_buf and rx_buf in ynl_sock is not
> initialized after allocation. This commit ensures the entire
> allocated memory is set to zero.
> 
> When asan is enabled, uninitialized bytes may contain poison values.
> This can cause failures e.g. when doing ynl_attr_put_str then poisoned
> bytes appear after the null terminator. As a result, tc filter addition
> may fail.

We add strings with the null-terminating char, AFAICT.
Do you mean that the poison value appears in the padding?

> Signed-off-by: Zahari Doychev <zahari.doychev@...ux.com>
> ---
>  tools/net/ynl/lib/ynl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/net/ynl/lib/ynl.c b/tools/net/ynl/lib/ynl.c
> index 2bcd781111d7..16a4815d6a49 100644
> --- a/tools/net/ynl/lib/ynl.c
> +++ b/tools/net/ynl/lib/ynl.c
> @@ -744,7 +744,7 @@ ynl_sock_create(const struct ynl_family *yf, struct ynl_error *yse)
>  	ys = malloc(sizeof(*ys) + 2 * YNL_SOCKET_BUFFER_SIZE);
>  	if (!ys)
>  		return NULL;
> -	memset(ys, 0, sizeof(*ys));
> +	memset(ys, 0, sizeof(*ys) + 2 * YNL_SOCKET_BUFFER_SIZE);

This is just clearing the buffer initially, it can be used for multiple
requests. This change is no good as is.