From 0f76408d8c1cb0979f4286dd23912e6e59784b35 Mon Sep 17 00:00:00 2001 From: DENG Qingfang Date: Thu, 19 Sep 2019 11:42:55 +0200 Subject: [PATCH] spi: spi-gpio: fix crash when num-chipselects is 0 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit If an spi-gpio was specified with num-chipselects = <0> in dts, kernel will crash: Unable to handle kernel paging request at virtual address 32697073 pgd = (ptrval) [32697073] *pgd=00000000 Internal error: Oops: 5 [# 1] SMP ARM Modules linked in: CPU: 2 PID: 1 Comm: swapper/0 Not tainted 4.19.72 #0 Hardware name: Generic DT based system PC is at validate_desc+0x28/0x80 LR is at gpiod_direction_output+0x14/0x128 ... [] (validate_desc) from [] (gpiod_direction_output+0x14/0x128) [] (gpiod_direction_output) from [] (spi_gpio_setup+0x58/0x64) [] (spi_gpio_setup) from [] (spi_setup+0x12c/0x148) [] (spi_setup) from [] (spi_add_device+0xbc/0x12c) [] (spi_add_device) from [] (spi_register_controller+0x838/0x924) [] (spi_register_controller) from [] (spi_bitbang_start+0x108/0x120) [] (spi_bitbang_start) from [] (spi_gpio_probe+0x314/0x338) [] (spi_gpio_probe) from [] (platform_drv_probe+0x34/0x70) The cause is spi_gpio_setup() did not check if the spi-gpio has chipselect pins before setting their direction and results in derefing an invalid pointer. The bug is spotted in kernel 4.19.72 on OpenWrt, and does not occur in 4.14. There is a similar fix upstream 249e2632dcd0509b8f8f296f5aabf4d48dfd6da8. Ref: https://patchwork.kernel.org/patch/11150619/ Cc: Linus Walleij Cc: stable@vger.kernel.org Signed-off-by: DENG Qingfang Signed-off-by: Petr Štetiar --- drivers/spi/spi-gpio.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) --- a/drivers/spi/spi-gpio.c +++ b/drivers/spi/spi-gpio.c @@ -242,10 +242,12 @@ static int spi_gpio_setup(struct spi_dev * The CS GPIOs have already been * initialized from the descriptor lookup. */ - cs = spi_gpio->cs_gpios[spi->chip_select]; - if (!spi->controller_state && cs) - status = gpiod_direction_output(cs, - !(spi->mode & SPI_CS_HIGH)); + if (spi_gpio->has_cs) { + cs = spi_gpio->cs_gpios[spi->chip_select]; + if (!spi->controller_state && cs) + status = gpiod_direction_output(cs, + !(spi->mode & SPI_CS_HIGH)); + } if (!status) status = spi_bitbang_setup(spi);