netdev - Re: [PATCH net-next] net: enable usercopy for skb_small_head

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Message-ID: <Y+SgcC4pRz42H83G@shredder>
Date:   Thu, 9 Feb 2023 09:27:44 +0200
From:   Ido Schimmel <idosch@...sch.org>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        eric.dumazet@...il.com, Soheil Hassas Yeganeh <soheil@...gle.com>,
        Alexander Duyck <alexanderduyck@...com>,
        syzbot <syzkaller@...glegroups.com>
Subject: Re: [PATCH net-next] net: enable usercopy for skb_small_head_cache

On Wed, Feb 08, 2023 at 02:25:08PM +0000, 'Eric Dumazet' via syzkaller wrote:
> syzbot and other bots reported that we have to enable
> user copy to/from skb->head. [1]
> 
> We can prevent access to skb_shared_info, which is a nice
> improvement over standard kmem_cache.
> 
> Layout of these kmem_cache objects is:
> 
> < SKB_SMALL_HEAD_HEADROOM >< struct skb_shared_info >

[...]

> 
> Fixes: bf9f1baa279f ("net: add dedicated kmem_cache for typical/small skb->head")
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Tested-by: Ido Schimmel <idosch@...dia.com>

Hit this one as well, patch solved the problem.

Thanks!