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From: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
To: Weiming Shi <bestswngs@gmail.com>,
	 netdev@vger.kernel.org,  linux-kernel@vger.kernel.org
Cc: willemdebruijn.kernel@gmail.com,  jasowang@redhat.com,
	 andrew+netdev@lunn.ch,  davem@davemloft.net,
	 edumazet@google.com,  kuba@kernel.org,  pabeni@redhat.com,
	 cong.wang@bytedance.com,  stable@vger.kernel.org,
	 xmei5@asu.edu,  Weiming Shi <bestswngs@gmail.com>
Subject: Re: [PATCH] tap: fix stack info leak in tap_ioctl() SIOCGIFHWADDR
Date: Wed, 20 May 2026 17:22:41 -0400	[thread overview]
Message-ID: <willemdebruijn.kernel.69dc20190163@gmail.com> (raw)
In-Reply-To: <20260520075736.3415676-3-bestswngs@gmail.com>

Weiming Shi wrote:
> In the SIOCGIFHWADDR path, tap_ioctl() copies 16 bytes of an
> uninitialised on-stack struct sockaddr_storage to userspace via
> ifr_hwaddr, but netif_get_mac_address() only writes sa_family and
> dev->addr_len (6 for Ethernet) bytes, leaving sa_data[6..13] uninitialised.
> 
> Those 8 trailing bytes leak kernel stack contents; SIOCGIFHWADDR on a
> macvtap chardev returns kernel .text and direct-map pointers, defeating
> KASLR.
> 
> Initialise ss at declaration.
> 
> Fixes: 3b23a32a6321 ("net: fix dev_ifsioc_locked() race condition")
> Reported-by: Xiang Mei <xmei5@asu.edu>
> Assisted-by: Claude:claude-opus-4-7
> Signed-off-by: Weiming Shi <bestswngs@gmail.com>

Reviewed-by: Willem de Bruijn <willemb@google.com>


  reply	other threads:[~2026-05-20 21:22 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-05-20  7:57 [PATCH] tap: fix stack info leak in tap_ioctl() SIOCGIFHWADDR Weiming Shi
2026-05-20 21:22 ` Willem de Bruijn [this message]
2026-05-20 21:30   ` Willem de Bruijn

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