Hi Wolfram, On Tue, Apr 16, 2024 at 2:35 PM Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx> wrote: > Clear the timer whenever 'chan_rx' is cleared to avoid an OOPS. > Currently, the driver only runs the timer when 'chan_rx' is set before. > However, it is good defensive programming to make sure the hrtimer is > always stopped before clearing the 'chan_rx' pointer. > > Reported-by: Dirk Behme <dirk.behme@xxxxxxxxxxxx> > Closes: https://lore.kernel.org/r/ee6c9e16-9f29-450e-81da-4a8dceaa8fc7@xxxxxxxxxxxx > Fixes: 9ab765566086 ("serial: sh-sci: Remove timer on shutdown of port") > Signed-off-by: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx> Thanks for your patch! > Locking needs to be double-checked here. This patch is mainly calling > for opinions. I do think you need to cancel the timer: even when not restarting the timer in sci_dma_rx_complete() due to a DMA failure, the previous timer may still be running, and will cause a NULL pointer dereference on s->chan_rx on timer expiry. > --- a/drivers/tty/serial/sh-sci.c > +++ b/drivers/tty/serial/sh-sci.c > @@ -1262,6 +1262,7 @@ static void sci_dma_rx_chan_invalidate(struct sci_port *s) > { > unsigned int i; > > + hrtimer_cancel(&s->rx_timer); Is it safe to do this unconditionally on shutdown (cfr. the old check for s->chan_rx_saved)? > s->chan_rx = NULL; > for (i = 0; i < ARRAY_SIZE(s->cookie_rx); i++) > s->cookie_rx[i] = -EINVAL; > @@ -2242,14 +2243,6 @@ static void sci_shutdown(struct uart_port *port) > scr & (SCSCR_CKE1 | SCSCR_CKE0 | s->hscif_tot)); > uart_port_unlock_irqrestore(port, flags); > > -#ifdef CONFIG_SERIAL_SH_SCI_DMA > - if (s->chan_rx_saved) { > - dev_dbg(port->dev, "%s(%d) deleting rx_timer\n", __func__, > - port->line); > - hrtimer_cancel(&s->rx_timer); > - } > -#endif > - > if (s->rx_trigger > 1 && s->rx_fifo_timeout > 0) > del_timer_sync(&s->rx_fifo_timer); > sci_free_irq(s); Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
