[PATCH 1/1] spi: fix use after free in of_spi_notify

[PATCH 1/1] spi: fix use after free in of_spi_notify

[Xiaohui Zhang]

We can't use "ctlr->dev" after it has been freed.

Signed-off-by: Xiaohui Zhang <xiaohuizhang@ruc.edu.cn>
---
 drivers/spi/spi.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index b9e2c7e7c580..dadfcdc6c38f 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -4198,14 +4198,15 @@ static int of_spi_notify(struct notifier_block *nb, unsigned long action,
 		}
 
 		spi = of_register_spi_device(ctlr, rd->dn);
-		put_device(&ctlr->dev);
 
 		if (IS_ERR(spi)) {
 			pr_err("%s: failed to create for '%pOF'\n",
 					__func__, rd->dn);
+			put_device(&ctlr->dev);
 			of_node_clear_flag(rd->dn, OF_POPULATED);
 			return notifier_from_errno(PTR_ERR(spi));
 		}
+		put_device(&ctlr->dev);
 		break;
 
 	case OF_RECONFIG_CHANGE_REMOVE:
-- 
2.17.1

Re: [PATCH 1/1] spi: fix use after free in of_spi_notify

[Mark Brown]

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On Tue, Jun 07, 2022 at 11:52:33PM +0800, Xiaohui Zhang wrote:
> We can't use "ctlr->dev" after it has been freed.

>  		spi = of_register_spi_device(ctlr, rd->dn);
> -		put_device(&ctlr->dev);
>  
>  		if (IS_ERR(spi)) {
>  			pr_err("%s: failed to create for '%pOF'\n",
>  					__func__, rd->dn);
> +			put_device(&ctlr->dev);
>  			of_node_clear_flag(rd->dn, OF_POPULATED);
>  			return notifier_from_errno(PTR_ERR(spi));
>  		}
> +		put_device(&ctlr->dev);
>  		break;

Could you be more explicit about where the problematic use of ctlr->dev
is please?

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