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SubjectRe: [PATCH] Revert "spi: simplify devm_spi_register_controller"
Date
On 12/07/2022 14:55, Yang Yingliang wrote:
> This reverts commit 59ebbe40fb51e307032ae7f63b2749fad2d4635a.
>
> If devm_add_action() fails in devm_add_action_or_reset(),
> devm_spi_unregister() will be called, it decreases the
> refcount of 'ctlr->dev' to 0, then it will cause uaf in
> the drivers that calling spi_put_controller() in error path.

Whether a revert is the right fix or not, this is the same
conclusion I came to reading your patch for my driver & on
that basis:

Reviewed-by: Conor Dooley <conor.dooley@microchip.com>

Seems like the master variant of this is used over 40 times:
rg "(?s)devm_spi_register_master.*master_put" drivers/spi --multiline -l

>
> Fixes: 59ebbe40fb51 ("spi: simplify devm_spi_register_controller")
> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
> ---
> drivers/spi/spi.c | 19 ++++++++++++++-----
> 1 file changed, 14 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
> index dc1a324e3271..ef751ccd65be 100644
> --- a/drivers/spi/spi.c
> +++ b/drivers/spi/spi.c
> @@ -3130,9 +3130,9 @@ int spi_register_controller(struct spi_controller *ctlr)
> }
> EXPORT_SYMBOL_GPL(spi_register_controller);
>
> -static void devm_spi_unregister(void *ctlr)
> +static void devm_spi_unregister(struct device *dev, void *res)
> {
> - spi_unregister_controller(ctlr);
> + spi_unregister_controller(*(struct spi_controller **)res);
> }
>
> /**
> @@ -3151,13 +3151,22 @@ static void devm_spi_unregister(void *ctlr)
> int devm_spi_register_controller(struct device *dev,
> struct spi_controller *ctlr)
> {
> + struct spi_controller **ptr;
> int ret;
>
> + ptr = devres_alloc(devm_spi_unregister, sizeof(*ptr), GFP_KERNEL);
> + if (!ptr)
> + return -ENOMEM;
> +
> ret = spi_register_controller(ctlr);
> - if (ret)
> - return ret;
> + if (!ret) {
> + *ptr = ctlr;
> + devres_add(dev, ptr);
> + } else {
> + devres_free(ptr);
> + }
>
> - return devm_add_action_or_reset(dev, devm_spi_unregister, ctlr);
> + return ret;
> }
> EXPORT_SYMBOL_GPL(devm_spi_register_controller);
>
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