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([2a02:3033:264:3f6c:c824:546f:eed:ab8a]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ae353ca201asm871356066b.150.2025.07.01.06.22.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 01 Jul 2025 06:22:56 -0700 (PDT) Message-ID: Date: Tue, 1 Jul 2025 15:22:54 +0200 Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] net: usb: usbnet: fix use-after-free in race on workqueue To: Paolo Abeni , "Peter GJ. Park" , Oliver Neukum , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski Cc: netdev@vger.kernel.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org References: <20250625-usbnet-uaf-fix-v1-1-421eb05ae6ea@samsung.com> <87a7f8a6-71b1-4b90-abc7-0a680f2a99cf@redhat.com> Content-Language: en-US From: Oliver Neukum In-Reply-To: <87a7f8a6-71b1-4b90-abc7-0a680f2a99cf@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hi, On 26.06.25 11:21, Paolo Abeni wrote: >> drivers/net/usb/usbnet.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c >> index c04e715a4c2ade3bc5587b0df71643a25cf88c55..3c5d9ba7fa6660273137c80106746103f84f5a37 100644 >> --- a/drivers/net/usb/usbnet.c >> +++ b/drivers/net/usb/usbnet.c >> @@ -1660,6 +1660,9 @@ void usbnet_disconnect (struct usb_interface *intf) >> usb_free_urb(dev->interrupt); >> kfree(dev->padding_pkt); >> >> + timer_delete_sync(&dev->delay); >> + tasklet_kill(&dev->bh); >> + cancel_work_sync(&dev->kevent); >> free_netdev(net); > This happens after unregister_netdev(), which calls usbnet_stop() that > already performs the above cleanup. How the race is supposed to take place? That is indeed a core question, which we really need an answer to. Do I interpret dev_close_many() correctly, if I state that the ndo_stop() method will _not_ be called if the device has never been opened? I am sorry to be a stickler here, but if that turns out to be true, usbnet is not the only driver that has this bug. TIA Oliver