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

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