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

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Message-ID: <20251117164201.4eab5834@kernel.org>
Date: Mon, 17 Nov 2025 16:42:01 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Jiefeng <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
Subject: Re: [PATCH] net: atlantic: fix fragment overflow handling in RX
 path

On Mon, 17 Nov 2025 19:38:54 +0800 Jiefeng wrote:
> From f78a25e62b4a0155beee0449536ba419feeddb75 Mon Sep 17 00:00:00 2001
> From: Jiefeng Zhang <jiefeng.z.zhang@...il.com>
> Date: Mon, 17 Nov 2025 16:17:37 +0800
> Subject: [PATCH] net: atlantic: fix fragment overflow handling in RX path
> 
> 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.

This submissions is not formatted correctly. Use git or b4 to send your
code. Please also make sure you read:
https://www.kernel.org/doc/html/next/process/maintainer-netdev.html

As for the patch -- what's the frag size the driver uses? If it's 
larger than max_mtu / 16 the overflow is impossible.