Commit 1979af10 authored by DENG Qingfang's avatar DENG Qingfang Committed by ynezz

kernel: 4.19: fix crash when setting up spi-gpio

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
 ...
 [<c0544db4>] (validate_desc) from [<c0545228>] (gpiod_direction_output+0x14/0x128)
 [<c0545228>] (gpiod_direction_output) from [<c05fa714>] (spi_gpio_setup+0x58/0x64)
 [<c05fa714>] (spi_gpio_setup) from [<c05f7258>] (spi_setup+0x12c/0x148)
 [<c05f7258>] (spi_setup) from [<c05f7330>] (spi_add_device+0xbc/0x12c)
 [<c05f7330>] (spi_add_device) from [<c05f7f74>] (spi_register_controller+0x838/0x924)
 [<c05f7f74>] (spi_register_controller) from [<c05fa494>] (spi_bitbang_start+0x108/0x120)
 [<c05fa494>] (spi_bitbang_start) from [<c05faa34>] (spi_gpio_probe+0x314/0x338)
 [<c05faa34>] (spi_gpio_probe) from [<c05a844c>] (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 and does not occur in 4.14.

There is a similar fix upstream in kernel 5.2 in commit 249e2632dcd0
("spi: gpio: Don't request CS GPIO in DT use-case").

Ref: https://patchwork.kernel.org/patch/11150619/Signed-off-by: default avatarDENG Qingfang <dengqf6@mail2.sysu.edu.cn>
[use upstream patch, moved from hack to pending dir, commit facelift]
Signed-off-by: ynezz's avatarPetr Štetiar <ynezz@true.cz>
parent c933b6d2
From 0f76408d8c1cb0979f4286dd23912e6e59784b35 Mon Sep 17 00:00:00 2001
From: DENG Qingfang <dqfext@gmail.com>
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
...
[<c0544db4>] (validate_desc) from [<c0545228>] (gpiod_direction_output+0x14/0x128)
[<c0545228>] (gpiod_direction_output) from [<c05fa714>] (spi_gpio_setup+0x58/0x64)
[<c05fa714>] (spi_gpio_setup) from [<c05f7258>] (spi_setup+0x12c/0x148)
[<c05f7258>] (spi_setup) from [<c05f7330>] (spi_add_device+0xbc/0x12c)
[<c05f7330>] (spi_add_device) from [<c05f7f74>] (spi_register_controller+0x838/0x924)
[<c05f7f74>] (spi_register_controller) from [<c05fa494>] (spi_bitbang_start+0x108/0x120)
[<c05fa494>] (spi_bitbang_start) from [<c05faa34>] (spi_gpio_probe+0x314/0x338)
[<c05faa34>] (spi_gpio_probe) from [<c05a844c>] (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 <linus.walleij@linaro.org>
Cc: stable@vger.kernel.org
Signed-off-by: DENG Qingfang <dqfext@gmail.com>
Signed-off-by: Petr Štetiar <ynezz@true.cz>
---
drivers/spi/spi-gpio.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/drivers/spi/spi-gpio.c b/drivers/spi/spi-gpio.c
index 088772ebef9b..57d5b6dc0dd0 100644
--- a/drivers/spi/spi-gpio.c
+++ b/drivers/spi/spi-gpio.c
@@ -242,10 +242,12 @@ static int spi_gpio_setup(struct spi_device *spi)
* 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);
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