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([175.159.214.250]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2bf239e8059sm93792055ad.9.2026.06.01.00.55.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 01 Jun 2026 00:55:28 -0700 (PDT) From: Junzhe Li To: gregkh@linuxfoundation.org Cc: linux-usb@vger.kernel.org Subject: [PATCH] usb: misc: ldusb: fix ordering of usb_deregister_dev() and usb_set_intfdata() Date: Mon, 1 Jun 2026 15:55:24 +0800 Message-Id: <20260601075524.136957-1-ginger.jzllee@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit In ld_usb_disconnect(), usb_set_intfdata(interface, NULL) was called before usb_deregister_dev(interface, &ld_usb_class). This opens a race window with usb_open() in the USB core: T0 (ld_usb_disconnect) T1 (usb_open) -------------------------- ------------------------- fops = usb_minors[minor] [t0] /* fops still valid here */ file->f_op->open(inode, file) ld_usb_open() dev = usb_get_intfdata() [t1] if (!dev) return -ENODEV; usb_set_intfdata(iface, NULL) [t2] access dev->mutex [t3] /* dev is NULL! */ usb_deregister_dev() usb_minors[minor] = NULL [t4] Because t0 precedes t1 precedes t2 precedes t3 precedes t4, T1 can obtain the file_operations pointer for the device (t0, while the minor is still registered), then continue into ld_usb_open() where it calls usb_get_intfdata() and gets NULL back, leading to a NULL dereference. The intuition is that the global exposure to the 'usb_minors' should be disabled first, so that subsequent nullification of the interface data pointer can be regarded as a local cleanup. Fix the race by calling usb_deregister_dev() first, which removes the device from usb_minors[] before the interface data pointer is cleared. Any concurrent usb_open() that arrives after usb_deregister_dev() returns will fail to look up the fops and will never reach ld_usb_open(). Reported-by: Junzhe Li Closes: https://lore.kernel.org/linux-usb/2026060157-pettiness-corporal-05eb@gregkh/ Signed-off-by: Junzhe Li --- drivers/usb/misc/ldusb.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/usb/misc/ldusb.c b/drivers/usb/misc/ldusb.c index c74f142f6637..ba65de2d4808 100644 --- a/drivers/usb/misc/ldusb.c +++ b/drivers/usb/misc/ldusb.c @@ -756,13 +756,14 @@ static void ld_usb_disconnect(struct usb_interface *intf) int minor; dev = usb_get_intfdata(intf); - usb_set_intfdata(intf, NULL); minor = intf->minor; /* give back our minor */ usb_deregister_dev(intf, &ld_usb_class); + usb_set_intfdata(intf, NULL); + usb_poison_urb(dev->interrupt_in_urb); usb_poison_urb(dev->interrupt_out_urb); -- 2.34.1