linux-kernel - Re: [PATCH net v4 2/2] net: sched: act_ife: initialize struct tc

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Message-ID: <CANn89iLZ6yHEga7zK7Ekcn=pPjS_3LZ1ixWbXQ_hmKtF9cmqcw@mail.gmail.com>
Date: Sun, 9 Nov 2025 01:31:37 -0800
From: Eric Dumazet <edumazet@...gle.com>
To: Ranganath V N <vnranganath.20@...il.com>
Cc: davem@...emloft.net, david.hunter.linux@...il.com, horms@...nel.org, 
	jhs@...atatu.com, jiri@...nulli.us, khalid@...nel.org, kuba@...nel.org, 
	pabeni@...hat.com, xiyou.wangcong@...il.com, linux-kernel@...r.kernel.org, 
	netdev@...r.kernel.org, skhan@...uxfoundation.org, 
	syzbot+0c85cae3350b7d486aee@...kaller.appspotmail.com
Subject: Re: [PATCH net v4 2/2] net: sched: act_ife: initialize struct tc_ife
 to fix KMSAN kernel-infoleak

On Sun, Nov 9, 2025 at 1:14 AM Ranganath V N <vnranganath.20@...il.com> 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.
>
> This change silences the KMSAN report and prevents potential information
> leaks from the kernel memory.
>
> This fix has been tested and validated by syzbot. This patch closes the
> bug reported at the following syzkaller link and ensures no infoleak.
>
> Reported-by: syzbot+0c85cae3350b7d486aee@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=0c85cae3350b7d486aee
> Tested-by: syzbot+0c85cae3350b7d486aee@...kaller.appspotmail.com
> Fixes: ef6980b6becb ("introduce IFE action")
> Signed-off-by: Ranganath V N <vnranganath.20@...il.com>

Reviewed-by: Eric Dumazet <edumazet@...gle.com>