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Sun, 12 Jul 2026 22:38:26 -0700 (PDT) Received: from HEXER.localdomain ([175.157.29.69]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-313b4b97661sm32915270eec.7.2026.07.12.22.38.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 12 Jul 2026 22:38:26 -0700 (PDT) From: Kanishka De Silva To: gregkh@linuxfoundation.org Cc: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, Kanishka De Silva , stable@vger.kernel.org Subject: [PATCH] usb: adutux: fix unlocked read_buffer_length write in adu_open() Date: Mon, 13 Jul 2026 11:07:37 +0530 Message-ID: <20260713053737.912-1-kpskanna1915@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026071358-illusion-basics-1146@gregkh> References: <2026071358-illusion-basics-1146@gregkh> Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit adu_open() clears dev->read_buffer_length while holding only adutux_mutex, but every other path that touches this field (adu_interrupt_in_callback() and adu_read()) correctly holds dev->buflock, per the locking scheme documented at the top of this file. This is a data race: an IRQ callback incrementing read_buffer_length concurrently with adu_open() clearing it can have its update silently lost, corrupting buffer state. Take buflock around the reset to bring adu_open() in line with the documented locking contract. Cc: stable@vger.kernel.org Signed-off-by: Kanishka De Silva --- drivers/usb/misc/adutux.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/usb/misc/adutux.c b/drivers/usb/misc/adutux.c index 369d0d2..606ef91 100644 --- a/drivers/usb/misc/adutux.c +++ b/drivers/usb/misc/adutux.c @@ -228,6 +228,7 @@ static int adu_open(struct inode *inode, struct file *file) { struct adu_device *dev = NULL; struct usb_interface *interface; + unsigned long flags; int subminor; int retval; @@ -265,7 +266,9 @@ static int adu_open(struct inode *inode, struct file *file) file->private_data = dev; /* initialize in direction */ + spin_lock_irqsave(&dev->buflock, flags); dev->read_buffer_length = 0; + spin_unlock_irqrestore(&dev->buflock, flags); /* fixup first read by having urb waiting for it */ usb_fill_int_urb(dev->interrupt_in_urb, dev->udev, -- 2.43.0