linux-kernel - Re: [PATCH v2] coresight: etm4x: Fix PID tracing when perf is run in an init PID namespace

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Message-ID: <20241013145524.GB45976@debian-dev>
Date: Sun, 13 Oct 2024 22:55:24 +0800
From: Leo Yan <leo.yan@...ux.dev>
To: Julien Meunier <julien.meunier@...ia.com>
Cc: Suzuki K Poulose <suzuki.poulose@....com>,
	Mike Leach <mike.leach@...aro.org>,
	James Clark <james.clark@...aro.org>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	stable@...r.kernel.org, coresight@...ts.linaro.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] coresight: etm4x: Fix PID tracing when perf is run in
 an init PID namespace

On Tue, Oct 08, 2024 at 10:02:25PM +0200, Julien Meunier wrote:
> The previous implementation limited the tracing capabilities when perf
> was run in the init PID namespace, making it impossible to trace
> applications in non-init PID namespaces.
> 
> This update improves the tracing process by verifying the event owner.
> This allows us to determine whether the user has the necessary
> permissions to trace the application.
> 
> Cc: stable@...r.kernel.org
> Fixes: aab473867fed ("coresight: etm4x: Don't trace PID for non-root PID namespace")
> Signed-off-by: Julien Meunier <julien.meunier@...ia.com>

Reviewed-by: Leo Yan <leo.yan@...ux.dev>

> ---
> Changes in v2:
> * Update comments
> ---
>  drivers/hwtracing/coresight/coresight-etm4x-core.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> index 66d44a404ad0..cf41c42399e1 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> @@ -693,9 +693,9 @@ static int etm4_parse_event_config(struct coresight_device *csdev,
>  		config->cfg |= TRCCONFIGR_TS;
>  	}
>  
> -	/* Only trace contextID when runs in root PID namespace */
> +	/* Only trace contextID when the event owner is in root PID namespace */
>  	if ((attr->config & BIT(ETM_OPT_CTXTID)) &&
> -	    task_is_in_init_pid_ns(current))
> +	    task_is_in_init_pid_ns(event->owner))
>  		/* bit[6], Context ID tracing bit */
>  		config->cfg |= TRCCONFIGR_CID;
>  
> @@ -709,8 +709,8 @@ static int etm4_parse_event_config(struct coresight_device *csdev,
>  			ret = -EINVAL;
>  			goto out;
>  		}
> -		/* Only trace virtual contextID when runs in root PID namespace */
> -		if (task_is_in_init_pid_ns(current))
> +		/* Only trace virtual contextID when the event owner is in root PID namespace */
> +		if (task_is_in_init_pid_ns(event->owner))
>  			config->cfg |= TRCCONFIGR_VMID | TRCCONFIGR_VMIDOPT;
>  	}
>  
> -- 
> 2.34.1
>