From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-lf1-f44.google.com (mail-lf1-f44.google.com [209.85.167.44]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1CFCD3451C1 for ; Tue, 21 Apr 2026 20:05:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.167.44 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776801957; cv=none; b=VPcw7SA0taUeToHKvcJLoqXGA6BZ+R0YQTjSNy8Sv44Gds1YrbWSUUa/xrmntRV1HD0uBB4PgX33DXEXHAB1mNuq1AbXwoS+pn1xAU5VqjcTJBFQaEInQJILfVw8cRCQW6g/1EFfPRHsM6nc3KKNLMUjao11/GVENRZj97NWeIc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776801957; c=relaxed/simple; bh=phULm1Ywed9W8M33T49Q6eS8se2Hvypqz3ZZdmbjhJM=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=tw4vr254WS5vqspxi3PDSAevI0CpOz0bCi6hJZo0WCe8A+fQDB7HFEMzOcuf5YieWoFKqIVLcHwWHWyE5pwLqX2tbx1mkgCJ2pNcHG+Zaoq02OW7U5GHs7Xj0/pXAAfErl6cfass/9DqbVNA+72DNApLHtxsXheIgyt6fFmQ0Yg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=LfboG50J; arc=none smtp.client-ip=209.85.167.44 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="LfboG50J" Received: by mail-lf1-f44.google.com with SMTP id 2adb3069b0e04-5a2c3dfb4a1so4861010e87.2 for ; Tue, 21 Apr 2026 13:05:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1776801954; x=1777406754; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:subject:cc:to:from:date:from:to:cc:subject:date :message-id:reply-to; bh=aK4izauZRRt/B/VXYkiUQKoI5K7lJzjxQ+RWvCNLSKk=; b=LfboG50JLmVr+cFmySs7f1HhhIew/QilyA0gHA4pXVhSqqQq9W5Qtv0lEGdXZTRrCl J7G3U5HWvFalRlTiwCLWoA2zNVZ+6DvHuSYO6d8aASyd8zfOzUVM1ki4N5GmKOjWjhee 5cgVNihXuWFoctzZ2ESS3+uLBPaZxqd4glk5C3Onm2qJgkRBnHRG/+Dyt3qR8sKXt9b2 ZJsWNY/JmB3IbVP8PGNQ19w51sjFmN/Y/9FKMuvWllbAtBlbhEHRQejuxVbCcYNfy0Hc 733uVBUofTxPifcjEpfYL3l/LbMP/9Fo10iz5YIv1vdHGdFCw9NC/9O8+K4ZmnhJtYSK 0hjw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1776801954; x=1777406754; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=aK4izauZRRt/B/VXYkiUQKoI5K7lJzjxQ+RWvCNLSKk=; b=c4EGZtoI4Qc/2+nzYVODWBNqb2QZMglnhuAgNNUSXn4UAe7BS3obDd9fHyzZBrnHDI +eoIzKw1tfMsWS3tyCBwZ5QOSJnS5q5RJ5j3wGv53Dt64VLQqSBd9o1nsquu4tU4l/SF iO3f6BPOF7rAyhoznmiVIZNqd/o4sS9CjO5KNherhzSYYN3x+QsygBuL2cA0fV8Z0njL 5BZkwFoH4Wo+Oghm4dTn5Uhe8cjlWobyacUw42jZe0jL3GlvXvSVnj4GlqmIPIGcEVbb 69YsEDqrIIF6Jw+UzfeV6aTR7Z+za3gVnb64Gwp6jVaKVHYyL/yTZJjbQ1I1ocZ6ZE75 tW9w== X-Forwarded-Encrypted: i=1; AFNElJ/fwoIzP9ggDGSerY+igisLbbckTXNe3aZAFwRZXvXv1pWvtkfB3X9LoA53eiuI8q3uq0Kx85zwp2iPT2w=@vger.kernel.org X-Gm-Message-State: AOJu0YzCtwNE6XZwcdcCTBOn1I8+X8y0tOvbglXfVJ/N2ZTswbM5LxhK akFcftWCB8muAvqRd587P4C21hWxWfz4wsRm2Dh4eVjoDr94r8qNJ2CR X-Gm-Gg: AeBDiet9cy+rtU0pwMDJvTUAhfAHaGfBabaZ0z53alpqc6E2AByd2V/3lbaZmjHgfAN SAhuXzFxQWIvCUdl3oUrnIs5TeysTJHHIOurlq5hsaRRbQ4oV5qB65F0rS3X/BmBZigwsrje5G+ v+SfboLSQFGb2Y4JU4MCkmMOdSdmSqfO1Ru2hcmEQ25bvuJaZCYlOUzAZ08fZNye7cpeD8JuM06 Tyx2l84VCerCQffaVs0G4vrM/uozeP91Ft8nxFicLxbzYg/PD2DGLKfetPuTMrYh20Qn5bId4ed JGdIW4CWmnFkHzT5Ip7WbkjwvwFuUoN+iBizA5twUof/arBdao0EwIWybyJyEz7fbEfwdFlx0yS uS5lT/ooL2Th+3KlEWrBRPHPIlBf6lhGRqBQ60kb7ISvWrCzWf9u4/2ES2ScBxORUj5uNXw5+mz U/3RGHUGQv5ZS5tYpj9UqI89dRaG6VroBEqn++NGQZJO4= X-Received: by 2002:a05:6512:3b12:b0:5a3:f3a4:1aff with SMTP id 2adb3069b0e04-5a4172e87afmr5498771e87.38.1776801954040; Tue, 21 Apr 2026 13:05:54 -0700 (PDT) Received: from foxbook (bfh75.neoplus.adsl.tpnet.pl. [83.28.45.75]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5a4187e11ecsm3934256e87.47.2026.04.21.13.05.51 (version=TLS1_2 cipher=AES128-SHA bits=128/128); Tue, 21 Apr 2026 13:05:52 -0700 (PDT) Date: Tue, 21 Apr 2026 22:05:47 +0200 From: Michal Pecio To: Morduan Zang Cc: petkan@nucleusys.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, andrew+netdev@lunn.ch, linux-usb@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, Zhan Jun , syzbot+3f46c095ac0ca048cb71@syzkaller.appspotmail.com Subject: Re: [PATCH] net: usb: rtl8150: fix use-after-free in rtl8150_start_xmit() Message-ID: <20260421220547.2f7f9d85.michal.pecio@gmail.com> In-Reply-To: <73ACB7391A6DE033+20260421110412.14795-1-zhangdandan@uniontech.com> References: <73ACB7391A6DE033+20260421110412.14795-1-zhangdandan@uniontech.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=US-ASCII Content-Transfer-Encoding: 7bit On Tue, 21 Apr 2026 19:04:12 +0800, Morduan Zang wrote: > From: Zhan Jun > > syzbot reported a KASAN slab-use-after-free read in rtl8150_start_xmit() > when accessing skb->len for tx statistics after usb_submit_urb() has > been called: > > BUG: KASAN: slab-use-after-free in rtl8150_start_xmit+0x71f/0x760 > drivers/net/usb/rtl8150.c:712 > Read of size 4 at addr ffff88810eb7a930 by task kworker/0:4/5226 > > The URB completion handler write_bulk_callback() frees the skb via > dev_kfree_skb_irq(dev->tx_skb). The URB may complete on another CPU > in softirq context before usb_submit_urb() returns in the submitter, > so by the time the submitter reads skb->len the skb has already been > queued to the per-CPU completion_queue and freed by net_tx_action(): > > CPU A (xmit) CPU B (USB completion softirq) > ------------ ------------------------------ > dev->tx_skb = skb; > usb_submit_urb() --+ > |-------> write_bulk_callback() > | dev_kfree_skb_irq(dev->tx_skb) > | net_tx_action() > | napi_skb_cache_put() <-- free > netdev->stats.tx_bytes | > += skb->len; <-- UAF read > > Fix it by caching skb->len before submitting the URB and using the > cached value when updating the tx_bytes counter. Question: Is it correct that ETH_ZLEN padding isn't counted in tx_bytes? > This mirrors the fix pattern used by other USB network drivers. Which ones? I looked at a few and they either: - appear to have the same bug (kaweth) - update stats on URB completion, right before freeing skb - copy data out of skb, update stats, free skb before URB completion Regards, Michal