]> www.infradead.org Git - users/jedix/linux-maple.git/commit
tty: serial: fsl_lpuart: fix race on RX DMA shutdown
authorAlexander Sverdlin <alexander.sverdlin@siemens.com>
Thu, 9 Mar 2023 13:43:02 +0000 (14:43 +0100)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 6 Apr 2023 10:10:36 +0000 (12:10 +0200)
commit954fc9931f0aabf272b5674cf468affdd88d3a36
tree06ac5b3554f8f78b279b523798b1ef93196116df
parent3a4d6f959caaf5bc24779fe5846a191482df524c
tty: serial: fsl_lpuart: fix race on RX DMA shutdown

[ Upstream commit 1be6f2b15f902c02e055ae0b419ca789200473c9 ]

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.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
drivers/tty/serial/fsl_lpuart.c