This is a note to let you know that I've just added the patch titled
tty: serial: fsl_lpuart: fix race on RX DMA shutdown
to the 6.2-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tty-serial-fsl_lpuart-fix-race-on-rx-dma-shutdown.patch
and it can be found in the queue-6.2 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 1be6f2b15f902c02e055ae0b419ca789200473c9 Mon Sep 17 00:00:00 2001
From: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxxxx>
Date: Thu, 9 Mar 2023 14:43:02 +0100
Subject: tty: serial: fsl_lpuart: fix race on RX DMA shutdown
From: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230309134302.74940-2-alexander.sverdlin@xxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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 */
Patches currently in stable-queue which might be from alexander.sverdlin@xxxxxxxxxxx are
queue-6.2/tty-serial-fsl_lpuart-fix-race-on-rx-dma-shutdown.patch
