The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-4.14.y git checkout FETCH_HEAD git cherry-pick -x 1be6f2b15f902c02e055ae0b419ca789200473c9 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '167930351799217@kroah.com' --subject-prefix 'PATCH 4.14.y' HEAD^..
Possible dependencies:
1be6f2b15f90 ("tty: serial: fsl_lpuart: fix race on RX DMA shutdown") 8682ab0eea89 ("tty: serial: fsl_lpuart: switch to new dmaengine_terminate_* API") 4f5cb8c5e915 ("tty: serial: fsl_lpuart: enable wakeup source for lpuart") 374e01fa1304 ("serial: fsl_lpuart: Fix comment typo") b14109f302d0 ("tty: serial: fsl_lpuart: Use __maybe_unused instead of #if CONFIG_PM_SLEEP") 810bc0a5fafb ("tty: serial: fsl_lpuart: make coverity happy") d0e7600b914c ("tty: serial: fsl_lpuart: move dma_request_chan()") c2f448cff22a ("tty: serial: fsl_lpuart: add LS1028A support") a092ab25fdaa ("tty: serial: fsl_lpuart: fix DMA mapping") 159381df1442 ("tty: serial: fsl_lpuart: fix DMA operation when using IOMMU") 487ee861de17 ("tty: serial: fsl_lpuart: use the sg count from dma_map_sg") 352bd55e5dce ("tty: serial: fsl_lpuart: Introduce lpuart*_setup_watermark_enable()") 4ff69041eccf ("tty: serial: fsl_lpuart: Introduce lpuart32_configure()") fd60e8e4a701 ("tty: serial: fsl_lpuart: Introduce lpuart_rx_dma_startup()") 5982199ca071 ("tty: serial: fsl_lpuart: Introduce lpuart_tx_dma_startup()") 769d55c523f7 ("tty: serial: fsl_lpuart: Introduce lpuart_dma_shutdown()") 8a9b82422ff5 ("tty: serial: fsl_lpuart: Drop unnecessary lpuart*_stop_tx()") bcfa46bfb9b7 ("tty: serial: fsl_lpuart: Drop unnecessary extra parenthesis") d26454ee3c45 ("tty: serial: fsl_lpuart: Drop no-op bit opearation") 9bc19af9dacb ("tty: serial: fsl_lpuart: Flush HW FIFOs in .flush_buffer")
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 1be6f2b15f902c02e055ae0b419ca789200473c9 Mon Sep 17 00:00:00 2001 From: Alexander Sverdlin alexander.sverdlin@siemens.com Date: Thu, 9 Mar 2023 14:43:02 +0100 Subject: [PATCH] tty: serial: fsl_lpuart: fix race on RX DMA shutdown
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
diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c index f9e164abf920..56e6ba3250cd 100644 --- a/drivers/tty/serial/fsl_lpuart.c +++ b/drivers/tty/serial/fsl_lpuart.c @@ -1354,6 +1354,7 @@ static void lpuart_dma_rx_free(struct uart_port *port) 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; @@ -1813,7 +1814,6 @@ static int lpuart32_startup(struct uart_port *port) 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; } @@ -1973,10 +1973,8 @@ lpuart_set_termios(struct uart_port *port, struct ktermios *termios, * 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);
@@ -2210,10 +2208,8 @@ lpuart32_set_termios(struct uart_port *port, struct ktermios *termios, * 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);
@@ -3020,7 +3016,6 @@ static int lpuart_suspend(struct device *dev) * 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 */