From: Alexander Sverdlin alexander.sverdlin@siemens.com
commit 1be6f2b15f902c02e055ae0b419ca789200473c9 upstream.
From time to time DMA completion can come in the middle of DMA shutdown:
<process ctx>: <IRQ>: lpuart32_shutdown() lpuart_dma_shutdown() del_timer_sync() lpuart_dma_rx_complete() lpuart_copy_rx_to_tty() mod_timer() lpuart_dma_rx_free()
When the timer fires a bit later, sport->dma_rx_desc is NULL:
Unable to handle kernel NULL pointer dereference at virtual address 0000000000000004 pc : lpuart_copy_rx_to_tty+0xcc/0x5bc lr : lpuart_timer_func+0x1c/0x2c Call trace: lpuart_copy_rx_to_tty lpuart_timer_func call_timer_fn __run_timers.part.0 run_timer_softirq __do_softirq __irq_exit_rcu irq_exit handle_domain_irq gic_handle_irq call_on_irq_stack do_interrupt_handler ...
To fix this fold del_timer_sync() into lpuart_dma_rx_free() after dmaengine_terminate_sync() to make sure timer will not be re-started in lpuart_copy_rx_to_tty() <= lpuart_dma_rx_complete().
Fixes: 4a8588a1cf86 ("serial: fsl_lpuart: delete timer on shutdown") Cc: stable stable@kernel.org Signed-off-by: Alexander Sverdlin alexander.sverdlin@siemens.com Link: https://lore.kernel.org/r/20230309134302.74940-2-alexander.sverdlin@siemens.... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/tty/serial/fsl_lpuart.c | 11 +++-------- 1 file changed, 3 insertions(+), 8 deletions(-)
--- a/drivers/tty/serial/fsl_lpuart.c +++ b/drivers/tty/serial/fsl_lpuart.c @@ -1328,6 +1328,7 @@ static void lpuart_dma_rx_free(struct ua struct dma_chan *chan = sport->dma_rx_chan;
dmaengine_terminate_sync(chan); + del_timer_sync(&sport->lpuart_timer); dma_unmap_sg(chan->device->dev, &sport->rx_sgl, 1, DMA_FROM_DEVICE); kfree(sport->rx_ring.buf); sport->rx_ring.tail = 0; @@ -1762,7 +1763,6 @@ static int lpuart32_startup(struct uart_ static void lpuart_dma_shutdown(struct lpuart_port *sport) { if (sport->lpuart_dma_rx_use) { - del_timer_sync(&sport->lpuart_timer); lpuart_dma_rx_free(&sport->port); sport->lpuart_dma_rx_use = false; } @@ -1922,10 +1922,8 @@ lpuart_set_termios(struct uart_port *por * Since timer function acqures sport->port.lock, need to stop before * acquring same lock because otherwise del_timer_sync() can deadlock. */ - if (old && sport->lpuart_dma_rx_use) { - del_timer_sync(&sport->lpuart_timer); + if (old && sport->lpuart_dma_rx_use) lpuart_dma_rx_free(&sport->port); - }
spin_lock_irqsave(&sport->port.lock, flags);
@@ -2159,10 +2157,8 @@ lpuart32_set_termios(struct uart_port *p * Since timer function acqures sport->port.lock, need to stop before * acquring same lock because otherwise del_timer_sync() can deadlock. */ - if (old && sport->lpuart_dma_rx_use) { - del_timer_sync(&sport->lpuart_timer); + if (old && sport->lpuart_dma_rx_use) lpuart_dma_rx_free(&sport->port); - }
spin_lock_irqsave(&sport->port.lock, flags);
@@ -2962,7 +2958,6 @@ static int lpuart_suspend(struct device * cannot resume as expected, hence gracefully release the * Rx DMA path before suspend and start Rx DMA path on resume. */ - del_timer_sync(&sport->lpuart_timer); lpuart_dma_rx_free(&sport->port);
/* Disable Rx DMA to use UART port as wakeup source */