[PATCH] soc: ti: wkup_m3_ipc: Fix race condition with rproc_boot

[PATCH] soc: ti: wkup_m3_ipc: Fix race condition with rproc_boot

[Dave Gerlach]

Any user of wkup_m3_ipc calls wkup_m3_ipc_get to get a handle and this
checks the value of the static variable m3_ipc_state to see if the
wkup_m3 is ready. Currently this is populated during probe before
rproc_boot has been called, meaning there is a window of time that
wkup_m3_ipc_get can return a valid handle but the wkup_m3 itself is not
ready, leading to invalid IPC calls to the wkup_m3 and system
instability.

To avoid this, move the population of the m3_ipc_state variable until
after rproc_boot has succeeded to guarantee a valid and usable handle
is always returned.

Reported-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Dave Gerlach <d-gerlach@ti.com>
---
 drivers/soc/ti/wkup_m3_ipc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/soc/ti/wkup_m3_ipc.c b/drivers/soc/ti/wkup_m3_ipc.c
index 378369d9364a..e9ece45d7a33 100644
--- a/drivers/soc/ti/wkup_m3_ipc.c
+++ b/drivers/soc/ti/wkup_m3_ipc.c
@@ -419,6 +419,8 @@ static void wkup_m3_rproc_boot_thread(struct wkup_m3_ipc *m3_ipc)
 	ret = rproc_boot(m3_ipc->rproc);
 	if (ret)
 		dev_err(dev, "rproc_boot failed\n");
+	else
+		m3_ipc_state = m3_ipc;
 
 	do_exit(0);
 }
@@ -505,8 +507,6 @@ static int wkup_m3_ipc_probe(struct platform_device *pdev)
 		goto err_put_rproc;
 	}
 
-	m3_ipc_state = m3_ipc;
-
 	return 0;
 
 err_put_rproc:
-- 
2.20.1

Re: [PATCH] soc: ti: wkup_m3_ipc: Fix race condition with rproc_boot

[Tony Lindgren]

Hi,

* Dave Gerlach <d-gerlach@ti.com> [191211 20:02]:
> Any user of wkup_m3_ipc calls wkup_m3_ipc_get to get a handle and this
> checks the value of the static variable m3_ipc_state to see if the
> wkup_m3 is ready. Currently this is populated during probe before
> rproc_boot has been called, meaning there is a window of time that
> wkup_m3_ipc_get can return a valid handle but the wkup_m3 itself is not
> ready, leading to invalid IPC calls to the wkup_m3 and system
> instability.
> 
> To avoid this, move the population of the m3_ipc_state variable until
> after rproc_boot has succeeded to guarantee a valid and usable handle
> is always returned.

Santosh, do you want me to pick this one into my fixes branch?

Regards,

Tony


> Reported-by: Suman Anna <s-anna@ti.com>
> Signed-off-by: Dave Gerlach <d-gerlach@ti.com>
> ---
>  drivers/soc/ti/wkup_m3_ipc.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/soc/ti/wkup_m3_ipc.c b/drivers/soc/ti/wkup_m3_ipc.c
> index 378369d9364a..e9ece45d7a33 100644
> --- a/drivers/soc/ti/wkup_m3_ipc.c
> +++ b/drivers/soc/ti/wkup_m3_ipc.c
> @@ -419,6 +419,8 @@ static void wkup_m3_rproc_boot_thread(struct wkup_m3_ipc *m3_ipc)
>  	ret = rproc_boot(m3_ipc->rproc);
>  	if (ret)
>  		dev_err(dev, "rproc_boot failed\n");
> +	else
> +		m3_ipc_state = m3_ipc;
>  
>  	do_exit(0);
>  }
> @@ -505,8 +507,6 @@ static int wkup_m3_ipc_probe(struct platform_device *pdev)
>  		goto err_put_rproc;
>  	}
>  
> -	m3_ipc_state = m3_ipc;
> -
>  	return 0;
>  
>  err_put_rproc:
> -- 
> 2.20.1
> 

Re: [PATCH] soc: ti: wkup_m3_ipc: Fix race condition with rproc_boot

[santosh.shilimkar]

On 12/17/19 10:25 AM, Tony Lindgren wrote:
> Hi,
> 
> * Dave Gerlach <d-gerlach@ti.com> [191211 20:02]:
>> Any user of wkup_m3_ipc calls wkup_m3_ipc_get to get a handle and this
>> checks the value of the static variable m3_ipc_state to see if the
>> wkup_m3 is ready. Currently this is populated during probe before
>> rproc_boot has been called, meaning there is a window of time that
>> wkup_m3_ipc_get can return a valid handle but the wkup_m3 itself is not
>> ready, leading to invalid IPC calls to the wkup_m3 and system
>> instability.
>>
>> To avoid this, move the population of the m3_ipc_state variable until
>> after rproc_boot has succeeded to guarantee a valid and usable handle
>> is always returned.
> 
> Santosh, do you want me to pick this one into my fixes branch?
> 
Sure, go ahead.

Acked-by: Santosh Shilimkar <ssantosh@kernel.org>

Re: [PATCH] soc: ti: wkup_m3_ipc: Fix race condition with rproc_boot

[Tony Lindgren]

* santosh.shilimkar@oracle.com <santosh.shilimkar@oracle.com> [191217 18:33]:
> On 12/17/19 10:25 AM, Tony Lindgren wrote:
> > Hi,
> > 
> > * Dave Gerlach <d-gerlach@ti.com> [191211 20:02]:
> > > Any user of wkup_m3_ipc calls wkup_m3_ipc_get to get a handle and this
> > > checks the value of the static variable m3_ipc_state to see if the
> > > wkup_m3 is ready. Currently this is populated during probe before
> > > rproc_boot has been called, meaning there is a window of time that
> > > wkup_m3_ipc_get can return a valid handle but the wkup_m3 itself is not
> > > ready, leading to invalid IPC calls to the wkup_m3 and system
> > > instability.
> > > 
> > > To avoid this, move the population of the m3_ipc_state variable until
> > > after rproc_boot has succeeded to guarantee a valid and usable handle
> > > is always returned.
> > 
> > Santosh, do you want me to pick this one into my fixes branch?
> > 
> Sure, go ahead.
> 
> Acked-by: Santosh Shilimkar <ssantosh@kernel.org>

OK thanks applying into fixes.

Tony