From: Daniel Zahka <daniel.zahka@gmail.com>
To: Qihang <q.h.hack.winter@gmail.com>, netdev@vger.kernel.org
Cc: willemdebruijn.kernel@gmail.com, davem@davemloft.net,
edumazet@google.com, kuba@kernel.org, pabeni@redhat.com,
horms@kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH net] packet: use a consistent hard_header_len in send paths
Date: Tue, 21 Jul 2026 12:01:44 -0400 [thread overview]
Message-ID: <3e4b1552-57d4-42ad-a244-a91b74b8dae1@gmail.com> (raw)
In-Reply-To: <20260721084935.12312-1-q.h.hack.winter@gmail.com>
On 7/21/26 4:49 AM, Qihang wrote:
> packet_snd() and tpacket_snd() read dev->hard_header_len multiple times
> while building an skb. Device reconfiguration can change this value
> concurrently, for example through bonding device type changes.
>
> For SOCK_RAW, packet_snd() stores the first value in reserve, later
> allocates headroom using LL_RESERVED_SPACE(dev), and then subtracts
> reserve from the skb headroom. If hard_header_len decreases between the
> reads, the skb can be allocated with less headroom than reserve, moving
> skb->data before skb->head. The subsequent skb_copy_datagram_from_iter()
> can then attempt an out-of-bounds copy. Hardened usercopy catches this as
> a kernel memory overwrite attempt.
>
Wouldn't there be a similar issue in the SOCK_DGRAM path with
dev_hard_header() calling skb_push() after packet_alloc_skb()?
next prev parent reply other threads:[~2026-07-21 16:01 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-21 8:49 [PATCH net] packet: use a consistent hard_header_len in send paths Qihang
2026-07-21 16:01 ` Daniel Zahka [this message]
2026-07-22 14:26 ` Willem de Bruijn
2026-07-24 3:36 ` Qihang
2026-07-25 7:39 ` Willem de Bruijn
2026-07-26 9:21 ` [PATCH net v2] packet: use consistent header lengths in raw " Qihang
2026-07-26 15:21 ` Willem de Bruijn
2026-07-28 3:10 ` [PATCH net v3 0/2] packet: use consistent hard_header_len in " Qihang
2026-07-28 3:13 ` Qihang
2026-07-28 3:13 ` [PATCH net v3 1/2] packet: use consistent hard_header_len in non-ring " Qihang
2026-07-28 20:25 ` Willem de Bruijn
2026-07-28 3:13 ` [PATCH net v3 2/2] packet: use consistent hard_header_len in TX_RING send path Qihang
2026-07-28 20:26 ` Willem de Bruijn
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