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SubjectRe: [PATCH] mmc: core: Fix struct mmc_gpio corruption
Hi Marc,

On Tue, Jul 3, 2018 at 11:11 AM, Marc Zyngier <marc.zyngier@arm.com> wrote:
> I recently realised that something was amiss with /proc/interrupts
> on my cubietruck:
>
> 51: 0 0 GICv2 41 Level mv64xxx_i2c
> 59: 1047 0 GICv2 117 Level eth0
> 66: 2 0 sunxi_pio_edge 1 Edge XXXXX
>
> where XXXXX has some non-ASCII characters, while I was expecting:
>
> 66: 0 0 sunxi_pio_edge 1 Edge 1c0f000.mmc cd
>
> It turns out that the cd_debounce_delay_ms field was recently to
> struct mmc_gpio, and carefully placed at the one spot where it could
> cause damage: right *after* the zero-sized array that contains the
> associated label. This label ends up being passed to the IRQ
> subsystem, and then overwritten by the cd_debounce_delay_ms field.
>
> Funky!
>
> Let's move that field to a less crowded location.
>
> Fixes: bfd694d5e21c ("mmc: core: Add tunable delay before detecting card after card is inserted")
> Cc: Shawn Lin <shawn.lin@rock-chips.com>
> Cc: Linus Walleij <linus.walleij@linaro.org>
> Cc: Ulf Hansson <ulf.hansson@linaro.org>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
> drivers/mmc/core/slot-gpio.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/core/slot-gpio.c b/drivers/mmc/core/slot-gpio.c
> index ef05e0039378..1ccf9dc07395 100644
> --- a/drivers/mmc/core/slot-gpio.c
> +++ b/drivers/mmc/core/slot-gpio.c
> @@ -27,8 +27,8 @@ struct mmc_gpio {
> bool override_cd_active_level;
> irqreturn_t (*cd_gpio_isr)(int irq, void *dev_id);
> char *ro_label;
> - char cd_label[0];
> u32 cd_debounce_delay_ms;
> + char cd_label[0];

Ulf has already applied a fix for this:
https://git.kernel.org/pub/scm/linux/kernel/git/ulfh/mmc.git/commit/?h=fixes&id=60feca8f59a0bbdee9545ab52775cad0171151ff

which is more robust as it will give a gcc error when cd_label gets
moved in the future.

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