linux-kernel - Re: [PATCH net] net: atlantic: fix fragment overflow handling in RX path

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Message-ID: <20251118122430.65cc5738@kernel.org>
Date: Tue, 18 Nov 2025 12:24:30 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: jiefeng.z.zhang@...il.com
Cc: netdev@...r.kernel.org, davem@...emloft.net, pabeni@...hat.com,
 andrew+netdev@...n.ch, edumazet@...gle.com, linux-kernel@...r.kernel.org,
 irusskikh@...vell.com
Subject: Re: [PATCH net] net: atlantic: fix fragment overflow handling in RX
 path

On Tue, 18 Nov 2025 15:04:02 +0800 jiefeng.z.zhang@...il.com wrote:
> From: Jiefeng Zhang <jiefeng.z.zhang@...il.com>
> 
> The atlantic driver can receive packets with more than MAX_SKB_FRAGS (17)
> fragments when handling large multi-descriptor packets. This causes an
> out-of-bounds write in skb_add_rx_frag_netmem() leading to kernel panic.
> 
> The issue occurs because the driver doesn't check the total number of
> fragments before calling skb_add_rx_frag(). When a packet requires more
> than MAX_SKB_FRAGS fragments, the fragment index exceeds the array bounds.
> 
> Add a check in __aq_ring_rx_clean() to ensure the total number of fragments
> (including the initial header fragment and subsequent descriptor fragments)
> does not exceed MAX_SKB_FRAGS. If it does, drop the packet gracefully
> and increment the error counter.

First off, some basic Linux mailing list savoir vivre:
 - please don't top post
 - please don't resubmit your code within 24h of previous posting
 - please wait for a discussion to close before you send another version

Quoting your response:

https://lore.kernel.org/all/CADEc0q6iLdpwYsyGAwH4qzST8G7asjdqgR6+ymXMy1k0wRwhNQ@mail.gmail.com/

> I have used git send-email to send my code.
> 
> As for the patch --The aquantia/atlantic driver supports a maximum of
> AQ_CFG_SKB_FRAGS_MAX (32U) fragments, while the kernel limits the
> maximum number of fragments to MAX_SKB_FRAGS (17).

Frag count limits in drivers are usually for Tx not Rx.
Again, why do you think this driver can generate more frags than 17?
-- 
pw-bot: cr