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Date: Thu, 9 Apr 2026 20:03:28 +0100
From: Simon Horman <horms@kernel.org>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	linux-hams@vger.kernel.org, Yizhe Zhuang <yizhe@darknavy.com>,
	stable <stable@kernel.org>
Subject: Re: [PATCH net] netrom: do some basic forms of validation on
 incoming frames
Message-ID: <20260409190328.GS469338@kernel.org>
References: <2026040730-untagged-groin-bbb7@gregkh>
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In-Reply-To: <2026040730-untagged-groin-bbb7@gregkh>

On Tue, Apr 07, 2026 at 10:45:31AM +0200, Greg Kroah-Hartman wrote:
> There is a lack of much validation of frame size coming from a
> netrom-based device.  While these devices are "trusted" doing some
> sanity checks is good to at least keep the fuzzing tools happy when they
> stumble across this ancient protocol and light up with a range of bug
> reports.
> 
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Jakub Kicinski <kuba@kernel.org>
> Cc: Paolo Abeni <pabeni@redhat.com>
> Cc: Simon Horman <horms@kernel.org>
> Cc: linux-hams@vger.kernel.org
> Assisted-by: gregkh_clanker_2000
> Reviewed-by: Yizhe Zhuang <yizhe@darknavy.com>
> Cc: stable <stable@kernel.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Hi Greg 2000!

I expect that checking skb->len isn't sufficient here
and pskb_may_pull needs to be used to ensure that
the data is also available in the linear section of the skb.

Also, although I'm all for incremental enhancements,
I do suspect that similar problems exist in the call
chain of these functions.

...