From: Jakub Kicinski <kuba@kernel.org>
To: Jiayuan Chen <jiayuan.chen@linux.dev>
Cc: bpf@vger.kernel.org, netdev@vger.kernel.org,
andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com,
pabeni@redhat.com, horms@kernel.org, ricardo@marliere.net,
viro@zeniv.linux.org.uk, dmantipov@yandex.ru,
aleksander.lobakin@intel.com, linux-ppp@vger.kernel.org,
linux-kernel@vger.kernel.org, mrpre@163.com,
syzbot+853242d9c9917165d791@syzkaller.appspotmail.com
Subject: Re: [PATCH net-next v2 1/1] ppp: Fix KMSAN warning by initializing 2-byte header
Date: Mon, 24 Feb 2025 14:26:44 -0800 [thread overview]
Message-ID: <20250224142644.7c084e9e@kernel.org> (raw)
In-Reply-To: <20250221061219.295590-2-jiayuan.chen@linux.dev>
On Fri, 21 Feb 2025 14:12:19 +0800 Jiayuan Chen wrote:
> + /* Check if we should pass this packet.
> + * BPF filter instructions assume each PPP packet has a 4-byte
> + * header (e.g., those generated by libpcap), and then default
> + * to skipping the first 2 bytes at the beginning of the
> + * instruction. However, we still need to initialize these
> + * 2-byte new headers to prevent crafted BPF programs from
> + * reading them which would cause reading of uninitialized
> + * data. Here, we set the headers according to the RFC 1662.
> + */
> + *(u16 *)skb_push(skb, 2) = htons(0xff03);
The constant from the RFC deserves a #define or enum.
Looks like we may already need it in one other place:
drivers/net/wan/fsl_ucc_hdlc.h:#define DEFAULT_PPP_HEAD 0xff03
--
pw-bot: cr
next prev parent reply other threads:[~2025-02-24 22:26 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-02-21 6:12 [PATCH net-next v2 0/1] ppp: Fix KMSAN uninit-value warning with bpf Jiayuan Chen
2025-02-21 6:12 ` [PATCH net-next v2 1/1] ppp: Fix KMSAN warning by initializing 2-byte header Jiayuan Chen
2025-02-24 22:26 ` Jakub Kicinski [this message]
2025-02-24 23:20 ` Jiayuan Chen
2025-02-25 0:07 ` Jakub Kicinski
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