From: David Miller <davem@davemloft.net>
To: xie.he.0141@gmail.com
Cc: kuba@kernel.org, edumazet@google.com, ms@dev.tdt.de,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-x25@vger.kernel.org
Subject: Re: [PATCH] drivers/net/wan: lapb: Corrected the usage of skb_cow
Date: Fri, 24 Jul 2020 20:17:59 -0700 (PDT) [thread overview]
Message-ID: <20200724.201759.487082545769759347.davem@davemloft.net> (raw)
In-Reply-To: <20200724163347.57213-1-xie.he.0141@gmail.com>
From: Xie He <xie.he.0141@gmail.com>
Date: Fri, 24 Jul 2020 09:33:47 -0700
> This patch fixed 2 issues with the usage of skb_cow in LAPB drivers
> "lapbether" and "hdlc_x25":
>
> 1) After skb_cow fails, kfree_skb should be called to drop a reference
> to the skb. But in both drivers, kfree_skb is not called.
>
> 2) skb_cow should be called before skb_push so that is can ensure the
> safety of skb_push. But in "lapbether", it is incorrectly called after
> skb_push.
>
> More details about these 2 issues:
>
> 1) The behavior of calling kfree_skb on failure is also the behavior of
> netif_rx, which is called by this function with "return netif_rx(skb);".
> So this function should follow this behavior, too.
>
> 2) In "lapbether", skb_cow is called after skb_push. This results in 2
> logical issues:
> a) skb_push is not protected by skb_cow;
> b) An extra headroom of 1 byte is ensured after skb_push. This extra
> headroom has no use in this function. It also has no use in the
> upper-layer function that this function passes the skb to
> (x25_lapb_receive_frame in net/x25/x25_dev.c).
> So logically skb_cow should instead be called before skb_push.
>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Martin Schiller <ms@dev.tdt.de>
> Signed-off-by: Xie He <xie.he.0141@gmail.com>
Applied, thank you.
prev parent reply other threads:[~2020-07-25 3:17 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-24 16:33 [PATCH] drivers/net/wan: lapb: Corrected the usage of skb_cow Xie He
2020-07-25 3:17 ` David Miller [this message]
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