| Message ID | 1676288170-5493-1-git-send-email-quic_prashk@quicinc.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v4] usb: gadget: u_serial: Add null pointer check in gserial_resume | expand |
On Mon, Feb 13, 2023 at 05:06:10PM +0530, Prashanth K wrote: > Consider a case where gserial_disconnect has already cleared > gser->ioport. And if a wakeup interrupt triggers afterwards, > gserial_resume gets called, which will lead to accessing of > gser->ioport and thus causing null pointer dereference.Add > a null pointer check to prevent this. > > Added a static spinlock to prevent gser->ioport from becoming > null after the newly added check. > > Fixes: aba3a8d01d62 ("usb: gadget: u_serial: add suspend resume callbacks") > Signed-off-by: Prashanth K <quic_prashk@quicinc.com> > --- > v4: Added short comment about serial_port_lock. > > drivers/usb/gadget/function/u_serial.c | 27 +++++++++++++++++++++++---- > 1 file changed, 23 insertions(+), 4 deletions(-) > > diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c > index 840626e..3a6adf2 100644 > --- a/drivers/usb/gadget/function/u_serial.c > +++ b/drivers/usb/gadget/function/u_serial.c > @@ -82,6 +82,13 @@ > #define WRITE_BUF_SIZE 8192 /* TX only */ > #define GS_CONSOLE_BUF_SIZE 8192 > > +/* > + * Since all the spinlocks used in this driver is part of struct gs_port (port_lock). > + * Added a new static spinlock to prevent race conditions where gs_port is dereferenced > + * after marking as null. > + */ This comment could be a little shorter and more direct. Something like: /* Prevents race conditions when accessing gser->ioport */ or /* Prevents races between disconnect and resume for gser->ioport */ or even just /* Protects gser->ioport */ Everything else looks okay. Alan Stern > +static DEFINE_SPINLOCK(serial_port_lock); > + > /* console info */ > struct gs_console { > struct console console; > @@ -1375,8 +1382,10 @@ void gserial_disconnect(struct gserial *gser) > if (!port) > return; > > + spin_lock_irqsave(&serial_port_lock, flags); > + > /* tell the TTY glue not to do I/O here any more */ > - spin_lock_irqsave(&port->port_lock, flags); > + spin_lock(&port->port_lock); > > gs_console_disconnect(port); > > @@ -1391,7 +1400,8 @@ void gserial_disconnect(struct gserial *gser) > tty_hangup(port->port.tty); > } > port->suspended = false; > - spin_unlock_irqrestore(&port->port_lock, flags); > + spin_unlock(&port->port_lock); > + spin_unlock_irqrestore(&serial_port_lock, flags); > > /* disable endpoints, aborting down any active I/O */ > usb_ep_disable(gser->out); > @@ -1425,10 +1435,19 @@ EXPORT_SYMBOL_GPL(gserial_suspend); > > void gserial_resume(struct gserial *gser) > { > - struct gs_port *port = gser->ioport; > + struct gs_port *port; > unsigned long flags; > > - spin_lock_irqsave(&port->port_lock, flags); > + spin_lock_irqsave(&serial_port_lock, flags); > + port = gser->ioport; > + > + if (!port) { > + spin_unlock_irqrestore(&serial_port_lock, flags); > + return; > + } > + > + spin_lock(&port->port_lock); > + spin_unlock(&serial_port_lock); > port->suspended = false; > if (!port->start_delayed) { > spin_unlock_irqrestore(&port->port_lock, flags); > -- > 2.7.4 >
diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c index 840626e..3a6adf2 100644 --- a/drivers/usb/gadget/function/u_serial.c +++ b/drivers/usb/gadget/function/u_serial.c @@ -82,6 +82,13 @@ #define WRITE_BUF_SIZE 8192 /* TX only */ #define GS_CONSOLE_BUF_SIZE 8192 +/* + * Since all the spinlocks used in this driver is part of struct gs_port (port_lock). + * Added a new static spinlock to prevent race conditions where gs_port is dereferenced + * after marking as null. + */ +static DEFINE_SPINLOCK(serial_port_lock); + /* console info */ struct gs_console { struct console console; @@ -1375,8 +1382,10 @@ void gserial_disconnect(struct gserial *gser) if (!port) return; + spin_lock_irqsave(&serial_port_lock, flags); + /* tell the TTY glue not to do I/O here any more */ - spin_lock_irqsave(&port->port_lock, flags); + spin_lock(&port->port_lock); gs_console_disconnect(port); @@ -1391,7 +1400,8 @@ void gserial_disconnect(struct gserial *gser) tty_hangup(port->port.tty); } port->suspended = false; - spin_unlock_irqrestore(&port->port_lock, flags); + spin_unlock(&port->port_lock); + spin_unlock_irqrestore(&serial_port_lock, flags); /* disable endpoints, aborting down any active I/O */ usb_ep_disable(gser->out); @@ -1425,10 +1435,19 @@ EXPORT_SYMBOL_GPL(gserial_suspend); void gserial_resume(struct gserial *gser) { - struct gs_port *port = gser->ioport; + struct gs_port *port; unsigned long flags; - spin_lock_irqsave(&port->port_lock, flags); + spin_lock_irqsave(&serial_port_lock, flags); + port = gser->ioport; + + if (!port) { + spin_unlock_irqrestore(&serial_port_lock, flags); + return; + } + + spin_lock(&port->port_lock); + spin_unlock(&serial_port_lock); port->suspended = false; if (!port->start_delayed) { spin_unlock_irqrestore(&port->port_lock, flags);
Consider a case where gserial_disconnect has already cleared gser->ioport. And if a wakeup interrupt triggers afterwards, gserial_resume gets called, which will lead to accessing of gser->ioport and thus causing null pointer dereference.Add a null pointer check to prevent this. Added a static spinlock to prevent gser->ioport from becoming null after the newly added check. Fixes: aba3a8d01d62 ("usb: gadget: u_serial: add suspend resume callbacks") Signed-off-by: Prashanth K <quic_prashk@quicinc.com> --- v4: Added short comment about serial_port_lock. drivers/usb/gadget/function/u_serial.c | 27 +++++++++++++++++++++++---- 1 file changed, 23 insertions(+), 4 deletions(-)