netdev - Re: [PATCH v2] can: fix skb reference counting in j1939_session

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Message-ID: <Z0nAKU7gJAdyY_KN@pengutronix.de>
Date: Fri, 29 Nov 2024 14:22:49 +0100
From: Oleksij Rempel <o.rempel@...gutronix.de>
To: Marc Kleine-Budde <mkl@...gutronix.de>
Cc: Dmitry Antipov <dmantipov@...dex.ru>,
	Robin van der Gracht <robin@...tonic.nl>,
	Oliver Hartkopp <socketcan@...tkopp.net>, linux-can@...r.kernel.org,
	netdev@...r.kernel.org, lvc-project@...uxtesting.org,
	syzbot+d4e8dc385d9258220c31@...kaller.appspotmail.com
Subject: Re: [PATCH v2] can: fix skb reference counting in j1939_session_new()

On Fri, Nov 29, 2024 at 02:05:11PM +0100, Marc Kleine-Budde wrote:
> On 29.11.2024 13:59:28, Marc Kleine-Budde wrote:
> > On 29.11.2024 13:55:56, Oleksij Rempel wrote:
> > > On Tue, Nov 05, 2024 at 12:48:23PM +0300, Dmitry Antipov wrote:
> > > > Since 'j1939_session_skb_queue()' do an extra 'skb_get()' for each
> > > > new skb, I assume that the same should be done for an initial one
> > > > in 'j1939_session_new()' just to avoid refcount underflow.
> > > > 
> > > > Reported-by: syzbot+d4e8dc385d9258220c31@...kaller.appspotmail.com
> > > > Closes: https://syzkaller.appspot.com/bug?extid=d4e8dc385d9258220c31
> > > > Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol")
> > > > Signed-off-by: Dmitry Antipov <dmantipov@...dex.ru>
> > > 
> > > Tested-by: Oleksij Rempel <o.rempel@...gutronix.de>
> > > Acked-by: Oleksij Rempel <o.rempel@...gutronix.de>
> > 
> > Can you re-phrase the commit message. The "assume" is not appropriate :)
> 
> What about:
> 
> Since j1939_session_skb_queue() does an extra skb_get() for each new
> skb, do the same for the initial one in j1939_session_new() to avoid
> refcount underflow.

Sounds good. Thx!

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