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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH net] macsec: don't read an unset MAC header in macsec_encrypt() Message-ID: References: <20260703083634.2035145-1-4ncienth@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260703083634.2035145-1-4ncienth@gmail.com> 2026-07-03, 17:36:33 +0900, Daehyeon Ko wrote: > macsec_encrypt() reads the Ethernet header via eth_hdr(skb) > (skb->head + skb->mac_header) to memmove() the 12 source/destination MAC > bytes forward and make room for the SecTAG. > > On the AF_PACKET SOCK_RAW + PACKET_QDISC_BYPASS transmit path the skb > reaches the macsec ndo_start_xmit() with the MAC header unset, so > eth_hdr(skb) resolves to skb->head + (u16)~0 and the read is out of > bounds: a 12-byte heap over-read that is also emitted on the wire as the > frame's outer source/destination MAC. KASAN reports a slab-out-of-bounds > read in macsec_start_xmit() on 6.0; on current mainline a CONFIG_DEBUG_NET > build flags it as an unset mac header in skb_mac_header(). > > On the TX path the L2 header is at skb->data, so use skb_eth_hdr(), added > by commit 96cc4b69581d ("macvlan: do not assume mac_header is set in > macvlan_broadcast()") for exactly this purpose. > > Fixes: c09440f7dcb3 ("macsec: introduce IEEE 802.1AE driver") > Cc: stable@vger.kernel.org > Signed-off-by: Daehyeon Ko <4ncienth@gmail.com> > --- > drivers/net/macsec.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) Reviewed-by: Sabrina Dubroca -- Sabrina