netdev - Re: [PATCH v2 0/2] net: sched: act_ife: initialize struct tc

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Message-ID: <aQoIygv-7h4m21SG@horms.kernel.org>
Date: Tue, 4 Nov 2025 14:08:10 +0000
From: Simon Horman <horms@...nel.org>
To: Ranganath V N <vnranganath.20@...il.com>
Cc: Jamal Hadi Salim <jhs@...atatu.com>,
	Cong Wang <xiyou.wangcong@...il.com>, Jiri Pirko <jiri@...nulli.us>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	skhan@...uxfoundation.org, david.hunter.linux@...il.com,
	khalid@...nel.org,
	syzbot+0c85cae3350b7d486aee@...kaller.appspotmail.com
Subject: Re: [PATCH v2 0/2] net: sched: act_ife: initialize struct tc_ife to
 fix KMSAN kernel-infoleak

On Sat, Nov 01, 2025 at 06:04:46PM +0530, Ranganath V N wrote:
> Fix a KMSAN kernel-infoleak detected  by the syzbot .
> 
> [net?] KMSAN: kernel-infoleak in __skb_datagram_iter
> 
> In tcf_ife_dump(), the variable 'opt' was partially initialized using a
> designatied initializer. While the padding bytes are reamined
> uninitialized. nla_put() copies the entire structure into a
> netlink message, these uninitialized bytes leaked to userspace.
> 
> Initialize the structure with memset before assigning its fields
> to ensure all members and padding are cleared prior to beign copied.

Perhaps not important, but this seems to only describe patch 1/2.

> 
> Signed-off-by: Ranganath V N <vnranganath.20@...il.com>

Sorry for not looking more carefully at v1.

The presence of this padding seems pretty subtle to me.
And while I agree that your change fixes the problem described.
I wonder if it would be better to make things more obvious
by adding a 2-byte pad member to the structures involved.

...