[PATCH] mailbox: mailbox-test: set tdev->signal to NULL after freeing

[PATCH] mailbox: mailbox-test: set tdev->signal to NULL after freeing

[Sudeep Holla]

tdev->signal is not set NULL after it's freed. This will cause random
exceptions when the stale pointer is accessed after tdev->signal is
freed. Also, since tdev->signal allocation is skipped the next time
it's written, this leads to continuous fault finally leading to the
total death of the system.

Cc: Lee Jones <lee.jones@linaro.org>
Cc: Jassi Brar <jassisinghbrar@gmail.com>
Fixes: d1c2f87c9a8f ("mailbox: mailbox-test: Prevent memory leak")
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
---
 drivers/mailbox/mailbox-test.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/mailbox/mailbox-test.c b/drivers/mailbox/mailbox-test.c
index 58d04726cdd7..9ca96e9db6bf 100644
--- a/drivers/mailbox/mailbox-test.c
+++ b/drivers/mailbox/mailbox-test.c
@@ -133,6 +133,7 @@ static ssize_t mbox_test_message_write(struct file *filp,
 out:
 	kfree(tdev->signal);
 	kfree(tdev->message);
+	tdev->signal = NULL;

 	return ret < 0 ? ret : count;
 }
--
1.9.1

Re: [PATCH] mailbox: mailbox-test: set tdev->signal to NULL after freeing

[Sudeep Holla]

Hi Jassi, Lee,

On 24/05/16 17:12, Sudeep Holla wrote:
> tdev->signal is not set NULL after it's freed. This will cause random
> exceptions when the stale pointer is accessed after tdev->signal is
> freed. Also, since tdev->signal allocation is skipped the next time
> it's written, this leads to continuous fault finally leading to the
> total death of the system.
>
> Cc: Lee Jones <lee.jones@linaro.org>
> Cc: Jassi Brar <jassisinghbrar@gmail.com>

Can you review this ?

-- 
Regards,
Sudeep

Re: [PATCH] mailbox: mailbox-test: set tdev->signal to NULL after freeing

[Lee Jones]

On Tue, 24 May 2016, Sudeep Holla wrote:

> tdev->signal is not set NULL after it's freed. This will cause random
> exceptions when the stale pointer is accessed after tdev->signal is
> freed. Also, since tdev->signal allocation is skipped the next time
> it's written, this leads to continuous fault finally leading to the
> total death of the system.
> 
> Cc: Lee Jones <lee.jones@linaro.org>
> Cc: Jassi Brar <jassisinghbrar@gmail.com>
> Fixes: d1c2f87c9a8f ("mailbox: mailbox-test: Prevent memory leak")
> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> ---
>  drivers/mailbox/mailbox-test.c | 1 +
>  1 file changed, 1 insertion(+)

Strange there isn't a kfree_and_null() call.

Patch looks okay to me though:

Acked-by: Lee Jones <lee.jones@linaro.org>

> diff --git a/drivers/mailbox/mailbox-test.c b/drivers/mailbox/mailbox-test.c
> index 58d04726cdd7..9ca96e9db6bf 100644
> --- a/drivers/mailbox/mailbox-test.c
> +++ b/drivers/mailbox/mailbox-test.c
> @@ -133,6 +133,7 @@ static ssize_t mbox_test_message_write(struct file *filp,
>  out:
>  	kfree(tdev->signal);
>  	kfree(tdev->message);
> +	tdev->signal = NULL;
> 
>  	return ret < 0 ? ret : count;
>  }

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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