Re: [PATCH] mailbox: arm_mhu_db: Fix mhu_db_shutdown by replacing kfree with devm_kfree

From: Cristian Marussi <cristian.marussi@arm.com>
To: Sudeep Holla <sudeep.holla@arm.com>
Cc: linux-kernel@vger.kernel.org, Jassi Brar <jassisinghbrar@gmail.com>
Subject: Re: [PATCH] mailbox: arm_mhu_db: Fix mhu_db_shutdown by replacing kfree with devm_kfree
Date: Tue, 1 Dec 2020 10:37:05 +0000	[thread overview]
Message-ID: <20201201103705.GA8455@e120937-lin> (raw)
In-Reply-To: <20201130102804.2345083-1-sudeep.holla@arm.com>

Hi Sudeep,

fixes the crash for me.

Tested-by: Cristian Marussi <cristian.marussi@arm.com>
Reviewed-by: Cristian Marussi <cristian.marussi@arm.com>

Thanks

Cristian

On Mon, Nov 30, 2020 at 10:28:04AM +0000, Sudeep Holla wrote:
> The mhu_db_channel info is allocated per channel using devm_kzalloc from
> mhu_db_mbox_xlate which gets called from mbox_request_channel. However
> we are releasing the allocated mhu_db_channel info using plain kfree from
> mhu_db_shutdown which is called from mbox_free_channel.
> 
> This leads to random crashes when the channel is freed like below one:
> 
>   Unable to handle kernel paging request at virtual address 0080000400000008
>   [0080000400000008] address between user and kernel address ranges
>   Internal error: Oops: 96000044 [#1] PREEMPT SMP
>   Modules linked in: scmi_module(-)
>   CPU: 1 PID: 2212 Comm: rmmod Not tainted 5.10.0-rc5 #31
>   Hardware name: ARM LTD ARM Juno Development Platform/ARM Juno
>   	Development Platform, BIOS EDK II Nov 19 2020
>   pstate: 20000085 (nzCv daIf -PAN -UAO -TCO BTYPE=--)
>   pc : release_nodes+0x74/0x230
>   lr : devres_release_all+0x40/0x68
>   Call trace:
>    release_nodes+0x74/0x230
>    devres_release_all+0x40/0x68
>    device_release_driver_internal+0x12c/0x1f8
>    driver_detach+0x58/0xe8
>    bus_remove_driver+0x64/0xe0
>    driver_unregister+0x38/0x68
>    platform_driver_unregister+0x1c/0x28
>    scmi_driver_exit+0x38/0x44 [scmi_module]
>    __arm64_sys_delete_module+0x188/0x260
>    el0_svc_common.constprop.0+0x80/0x1a8
>    do_el0_svc+0x2c/0x98
>    el0_sync_handler+0x160/0x168
>    el0_sync+0x174/0x180
>   Code: 1400000d eb07009f 54000460 f9400486 (f90004a6)
>   ---[ end trace c55ffd306c140233 ]---
> 
> Fix it by replacing kfree with devm_kfree as required.
> 
> Fixes: 7002ca237b21 ("mailbox: arm_mhu: Add ARM MHU doorbell driver")
> Reported-by: Cristian Marussi <cristian.marussi@arm.com>
> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> ---
>  drivers/mailbox/arm_mhu_db.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/mailbox/arm_mhu_db.c b/drivers/mailbox/arm_mhu_db.c
> index 275efe4cca0c..8eb66c4ecf5b 100644
> --- a/drivers/mailbox/arm_mhu_db.c
> +++ b/drivers/mailbox/arm_mhu_db.c
> @@ -180,7 +180,7 @@ static void mhu_db_shutdown(struct mbox_chan *chan)
>  
>  	/* Reset channel */
>  	mhu_db_mbox_clear_irq(chan);
> -	kfree(chan->con_priv);
> +	devm_kfree(mbox->dev, chan->con_priv);
>  	chan->con_priv = NULL;
>  }
>  
> -- 
> 2.25.1
> 