Re: [Linux Kernel Bugs] KASAN: slab-use-after-free Read in cec_queue_msg_fh and 4 other crashes in the cec device (`cec_ioctl`)

[Hans Verkuil]

Hi Chenyuan,

On 30/01/2024 15:35, Hans Verkuil wrote:
> On 29/01/2024 04:03, Yang, Chenyuan wrote:
>> Hi Hans,
>>
>> Thanks a lot for this new patch!
>>
>> After applying this new patch in the latest kernel (hash: ecb1b8288dc7ccbdcb3b9df005fa1c0e0c0388a7) and fuzzing with Syzkaller, it seems that the hang still exists.
>> To help you better debug it, I attached the covered lines for the fuzz testing and the output of `git diff`. Hope this could help you.
>>
>> By the way, the syscall descriptions for CEC have been merged into the Syzkaller mainstream: https://github.com/google/syzkaller/blob/master/sys/linux/dev_cec.txt.
>>
>> Let me know if you need further information.
>>
>> Best,
>> Chenyuan
> 
> Here is another patch. This now time outs on all wait_for_completion calls
> and reports a WARN_ON and shows additional info. Hopefully this will give me
> better insight into what is going on.
> 
> Unfortunately I was unable to reproduce this issue on my VM, so I have to
> rely on you to run the test.

Did you have time to run the test with this patch? It would be very useful to
see the results.

Regards,

	Hans

> 
> Regards,
> 
> 	Hans
> 
> [PATCH] Test
> 
> Signed-off-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
> ---
> diff --git a/drivers/media/cec/core/cec-adap.c b/drivers/media/cec/core/cec-adap.c
> index 5741adf09a2e..b1951eb7f5bd 100644
> --- a/drivers/media/cec/core/cec-adap.c
> +++ b/drivers/media/cec/core/cec-adap.c
> @@ -935,9 +935,12 @@ int cec_transmit_msg_fh(struct cec_adapter *adap, struct cec_msg *msg,
>  	 * Release the lock and wait, retake the lock afterwards.
>  	 */
>  	mutex_unlock(&adap->lock);
> -	wait_for_completion_killable(&data->c);
> -	if (!data->completed)
> -		cancel_delayed_work_sync(&data->work);
> +	if (WARN_ON(wait_for_completion_killable_timeout(&data->c, msecs_to_jiffies(adap->xfer_timeout_ms + 1000)) <= 0)) {
> +		dprintk(0, "wfc1: %px %d%d%d%d %x\n", adap->kthread_config,
> +			adap->is_configuring, adap->is_configured,
> +			adap->is_enabled, adap->must_reconfigure, adap->phys_addr);
> +	}
> +	cancel_delayed_work_sync(&data->work);
>  	mutex_lock(&adap->lock);
> 
>  	/* Cancel the transmit if it was interrupted */
> @@ -1563,10 +1566,12 @@ static int cec_config_thread_func(void *arg)
>  			cec_transmit_msg_fh(adap, &msg, NULL, false);
>  		}
>  	}
> +	mutex_unlock(&adap->lock);
> +    call_void_op(adap, configured);
> +    mutex_lock(&adap->lock);
>  	adap->kthread_config = NULL;
>  	complete(&adap->config_completion);
>  	mutex_unlock(&adap->lock);
> -	call_void_op(adap, configured);
>  	return 0;
> 
>  unconfigure:
> @@ -1592,6 +1597,17 @@ static void cec_claim_log_addrs(struct cec_adapter *adap, bool block)
>  	if (WARN_ON(adap->is_configuring || adap->is_configured))
>  		return;
> 
> +	if (adap->kthread_config) {
> +		mutex_unlock(&adap->lock);
> +//		wait_for_completion(&adap->config_completion);
> +		if (WARN_ON(wait_for_completion_killable_timeout(&adap->config_completion, msecs_to_jiffies(10000)) <= 0)) {
> +			dprintk(0, "wfc2: %px %d%d%d%d %x\n", adap->kthread_config,
> +				adap->is_configuring, adap->is_configured,
> +				adap->is_enabled, adap->must_reconfigure, adap->phys_addr);
> +		}
> +		mutex_lock(&adap->lock);
> +	}
> +
>  	init_completion(&adap->config_completion);
> 
>  	/* Ready to kick off the thread */
> @@ -1599,11 +1615,17 @@ static void cec_claim_log_addrs(struct cec_adapter *adap, bool block)
>  	adap->kthread_config = kthread_run(cec_config_thread_func, adap,
>  					   "ceccfg-%s", adap->name);
>  	if (IS_ERR(adap->kthread_config)) {
> -		adap->kthread_config = NULL;
>  		adap->is_configuring = false;
> +		adap->kthread_config = NULL;
>  	} else if (block) {
>  		mutex_unlock(&adap->lock);
> -		wait_for_completion(&adap->config_completion);
> +		//wait_for_completion(&adap->config_completion);
> +		if (WARN_ON(wait_for_completion_killable_timeout(&adap->config_completion, msecs_to_jiffies(10000)) <= 0)) {
> +			dprintk(0, "wfc3: %px %d%d%d%d %x\n", adap->kthread_config,
> +				adap->is_configuring, adap->is_configured,
> +				adap->is_enabled, adap->must_reconfigure, adap->phys_addr);
> +
> +		}
>  		mutex_lock(&adap->lock);
>  	}
>  }
> diff --git a/drivers/media/cec/core/cec-api.c b/drivers/media/cec/core/cec-api.c
> index 67dc79ef1705..d64bb716f9c6 100644
> --- a/drivers/media/cec/core/cec-api.c
> +++ b/drivers/media/cec/core/cec-api.c
> @@ -664,6 +664,8 @@ static int cec_release(struct inode *inode, struct file *filp)
>  		list_del_init(&data->xfer_list);
>  	}
>  	mutex_unlock(&adap->lock);
> +
> +	mutex_lock(&fh->lock);
>  	while (!list_empty(&fh->msgs)) {
>  		struct cec_msg_entry *entry =
>  			list_first_entry(&fh->msgs, struct cec_msg_entry, list);
> @@ -681,6 +683,7 @@ static int cec_release(struct inode *inode, struct file *filp)
>  			kfree(entry);
>  		}
>  	}
> +	mutex_unlock(&fh->lock);
>  	kfree(fh);
> 
>  	cec_put_device(devnode);
>