Re: [PATCH 2/7] soc: aspeed: lpc-snoop: Don't disable channels that aren't enabled

Jean Delvare
2025-04-16T12:15:11Z

On Fri, 11 Apr 2025 10:38:32 +0930, Andrew Jeffery wrote:
> Mitigate e.g. the following:
>
> # echo 1e789080.lpc-snoop > /sys/bus/platform/drivers/aspeed-lpc-snoop/unbind
> ...
> [ 120.363594] Unable to handle kernel NULL pointer dereference at virtual address 00000004 when write
> [ 120.373866] [00000004] *pgd=00000000
> [ 120.377910] Internal error: Oops: 805 [#1] SMP ARM
> [ 120.383306] CPU: 1 UID: 0 PID: 315 Comm: sh Not tainted 6.15.0-rc1-00009-g926217bc7d7d-dirty #20 NONE
> ...
> [ 120.679543] Call trace:
> [ 120.679559] misc_deregister from aspeed_lpc_snoop_remove+0x84/0xac
> [ 120.692462] aspeed_lpc_snoop_remove from platform_remove+0x28/0x38
> [ 120.700996] platform_remove from device_release_driver_internal+0x188/0x200
> ...
>
> Fixes: 9f4f9ae81d0a ("drivers/misc: add Aspeed LPC snoop driver")
> Cc: stable@vger.kernel.org
> Cc: Jean Delvare <jdelvare@suse.de>
> Signed-off-by: Andrew Jeffery <andrew@codeconstruct.com.au>
> ---
> drivers/soc/aspeed/aspeed-lpc-snoop.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/drivers/soc/aspeed/aspeed-lpc-snoop.c b/drivers/soc/aspeed/aspeed-lpc-snoop.c
> index bfa770ec51a889260d11c26e675f3320bf710a54..e9d9a8e60a6f062c0b53c9c02e5d73768453998d 100644
> --- a/drivers/soc/aspeed/aspeed-lpc-snoop.c
> +++ b/drivers/soc/aspeed/aspeed-lpc-snoop.c
> @@ -58,6 +58,7 @@ struct aspeed_lpc_snoop_model_data {
> };
>
> struct aspeed_lpc_snoop_channel {
> + bool enabled;
> struct kfifo fifo;
> wait_queue_head_t wq;
> struct miscdevice miscdev;
> @@ -190,6 +191,9 @@ static int aspeed_lpc_enable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
> const struct aspeed_lpc_snoop_model_data *model_data =
> of_device_get_match_data(dev);
>
> + if (lpc_snoop->chan[channel].enabled)
> + return -EBUSY;

This isn't supposed to happen, right? WARN_ON() may be appropriate.

> +
> init_waitqueue_head(&lpc_snoop->chan[channel].wq);
> /* Create FIFO datastructure */
> rc = kfifo_alloc(&lpc_snoop->chan[channel].fifo,
> @@ -236,6 +240,8 @@ static int aspeed_lpc_enable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
> regmap_update_bits(lpc_snoop->regmap, HICRB,
> hicrb_en, hicrb_en);
>
> + lpc_snoop->chan[channel].enabled = true;
> +
> return 0;
>
> err_misc_deregister:
> @@ -248,6 +254,9 @@ static int aspeed_lpc_enable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
> static void aspeed_lpc_disable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
> int channel)
> {
> + if (!lpc_snoop->chan[channel].enabled)
> + return;
> +
> switch (channel) {
> case 0:
> regmap_update_bits(lpc_snoop->regmap, HICR5,
> @@ -263,6 +272,8 @@ static void aspeed_lpc_disable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
> return;
> }
>
> + lpc_snoop->chan[channel].enabled = false;
> + /* Consider improving safety wrt concurrent reader(s) */
> misc_deregister(&lpc_snoop->chan[channel].miscdev);
> kfifo_free(&lpc_snoop->chan[channel].fifo);
> }
>

Acked-by: Jean Delvare <jdelvare@suse.de>

--
Jean Delvare
SUSE L3 Support