From 24ca1fea8f2753bf33e1d458ec1ae5d9b7796a65 Mon Sep 17 00:00:00 2001 From: Johan Hovold Date: Tue, 23 Jun 2026 17:12:29 +0200 Subject: [PATCH] USB: serial: digi_acceleport: fix write buffer corruption The digi_write_inb_command() is supposed to wait for the write urb to become available or return an error, but instead it updates the transfer buffer and tries to resubmit the urb on timeout. To make things worse, for commands like break control where no timeout is used, the driver would corrupt the urb immediately due to a broken jiffies comparison (on 32-bit machines this takes five minutes of uptime to trigger due to INITIAL_JIFFIES). Fix this by adding the missing return on timeout and waiting indefinitely when no timeout has been specified as intended. This issue was (sort of) flagged by Sashiko when reviewing an unrelated change to the driver. Link: https://sashiko.dev/#/patchset/20260610132232.356139-1-johan%40kernel.org?part=11 Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Reviewed-by: Greg Kroah-Hartman Signed-off-by: Johan Hovold --- drivers/usb/serial/digi_acceleport.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/drivers/usb/serial/digi_acceleport.c b/drivers/usb/serial/digi_acceleport.c index 6899aebfd6ae..5f3a95682179 100644 --- a/drivers/usb/serial/digi_acceleport.c +++ b/drivers/usb/serial/digi_acceleport.c @@ -427,20 +427,22 @@ static int digi_write_inb_command(struct usb_serial_port *port, int len; struct digi_port *priv = usb_get_serial_port_data(port); unsigned char *data = port->write_urb->transfer_buffer; + unsigned long expire; unsigned long flags; dev_dbg(&port->dev, "digi_write_inb_command: TOP: port=%d, count=%d\n", priv->dp_port_num, count); if (timeout) - timeout += jiffies; - else - timeout = ULONG_MAX; + expire = jiffies + timeout; spin_lock_irqsave(&priv->dp_port_lock, flags); while (count > 0 && ret == 0) { - while (priv->dp_write_urb_in_use && - time_before(jiffies, timeout)) { + while (priv->dp_write_urb_in_use) { + if (timeout && time_after(jiffies, expire)) { + ret = -ETIMEDOUT; + break; + } cond_wait_interruptible_timeout_irqrestore( &priv->write_wait, DIGI_RETRY_TIMEOUT, &priv->dp_port_lock, flags); @@ -449,6 +451,9 @@ static int digi_write_inb_command(struct usb_serial_port *port, spin_lock_irqsave(&priv->dp_port_lock, flags); } + if (ret) + break; + /* len must be a multiple of 4 and small enough to */ /* guarantee the write will send buffered data first, */ /* so commands are in order with data and not split */