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[34.85.235.172]) by smtp.gmail.com with ESMTPSA id 00721157ae682-7cc996b7d54sm57824987b3.12.2026.05.20.14.22.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 May 2026 14:22:41 -0700 (PDT) Date: Wed, 20 May 2026 17:22:41 -0400 From: Willem de Bruijn To: Weiming Shi , 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 Message-ID: In-Reply-To: <20260520075736.3415676-3-bestswngs@gmail.com> References: <20260520075736.3415676-3-bestswngs@gmail.com> Subject: Re: [PATCH] tap: fix stack info leak in tap_ioctl() SIOCGIFHWADDR Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit 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 > Assisted-by: Claude:claude-opus-4-7 > Signed-off-by: Weiming Shi Reviewed-by: Willem de Bruijn