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

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Message-Id: <20241008200226.12229-1-julien.meunier@nokia.com>
Date: Tue,  8 Oct 2024 22:02:25 +0200
From: Julien Meunier <julien.meunier@...ia.com>
To: 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>,
	Leo Yan <leo.yan@...ux.dev>
Cc: stable@...r.kernel.org,
	coresight@...ts.linaro.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2] coresight: etm4x: Fix PID tracing when perf is run in an init PID namespace

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>
---
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