coresight: Don't use contextID with PID namespaces

index e8b4549e30e2..79e1ad860d8a 100644
@@ -168,8 +168,6 @@
  * @seq_curr_state: current value of the sequencer register.
  * @ctxid_idx: index for the context ID registers.
  * @ctxid_pid: value for the context ID to trigger on.
- * @ctxid_vpid:	Virtual PID seen by users if PID namespace is enabled, otherwise
- *		the same value of ctxid_pid.
  * @ctxid_mask: mask applicable to all the context IDs.
  * @sync_freq:	Synchronisation frequency.
  * @timestamp_event: Defines an event that requests the insertion

@@ -202,7 +200,6 @@ struct etm_config {
 	u32				seq_curr_state;
 	u8				ctxid_idx;
 	u32				ctxid_pid[ETM_MAX_CTXID_CMP];
-	u32				ctxid_vpid[ETM_MAX_CTXID_CMP];
 	u32				ctxid_mask;
 	u32				sync_freq;
 	u32				timestamp_event;

82 lines not on this page · raw message

index 15ed64d51a5b..7c74263c333d 100644
@@ -230,10 +230,8 @@ void etm_set_default(struct etm_config *config)
 
 	config->seq_curr_state = 0x0;
 	config->ctxid_idx = 0x0;
-	for (i = 0; i < ETM_MAX_CTXID_CMP; i++) {
+	for (i = 0; i < ETM_MAX_CTXID_CMP; i++)
 		config->ctxid_pid[i] = 0x0;
-		config->ctxid_vpid[i] = 0x0;
-	}
 
 	config->ctxid_mask = 0x0;
 	/* Setting default to 1024 as per TRM recommendation */

index 4eb8da785ce0..a0365e23678e 100644
@@ -4,6 +4,7 @@
  * Author: Mathieu Poirier <[email protected]>
  */
 
+#include <linux/pid_namespace.h>
 #include <linux/pm_runtime.h>
 #include <linux/sysfs.h>
 #include "coresight-etm4x.h"

@@ -250,10 +251,8 @@ static ssize_t reset_store(struct device *dev,
 	}
 
 	config->ctxid_idx = 0x0;
-	for (i = 0; i < drvdata->numcidc; i++) {
+	for (i = 0; i < drvdata->numcidc; i++)
 		config->ctxid_pid[i] = 0x0;
-		config->ctxid_vpid[i] = 0x0;
-	}
 
 	config->ctxid_mask0 = 0x0;
 	config->ctxid_mask1 = 0x0;

@@ -1637,9 +1636,16 @@ static ssize_t ctxid_pid_show(struct device *dev,
 	struct etmv4_drvdata *drvdata = dev_get_drvdata(dev->parent);
 	struct etmv4_config *config = &drvdata->config;
 
+	/*
+	 * Don't use contextID tracing if coming from a PID namespace.  See
+	 * comment in ctxid_pid_store().
+	 */
+	if (task_active_pid_ns(current) != &init_pid_ns)
+		return -EINVAL;
+
 	spin_lock(&drvdata->spinlock);
 	idx = config->ctxid_idx;
-	val = (unsigned long)config->ctxid_vpid[idx];
+	val = (unsigned long)config->ctxid_pid[idx];
 	spin_unlock(&drvdata->spinlock);
 	return scnprintf(buf, PAGE_SIZE, "%#lx\n", val);
 }

@@ -1649,26 +1655,35 @@ static ssize_t ctxid_pid_store(struct device *dev,
 			       const char *buf, size_t size)
 {
 	u8 idx;
-	unsigned long vpid, pid;
+	unsigned long pid;
 	struct etmv4_drvdata *drvdata = dev_get_drvdata(dev->parent);
 	struct etmv4_config *config = &drvdata->config;
 
 	/*
+	 * When contextID tracing is enabled the tracers will insert the
+	 * value found in the contextID register in the trace stream.  But if
+	 * a process is in a namespace the PID of that process as seen from the
+	 * namespace won't be what the kernel sees, something that makes the
+	 * feature confusing and can potentially leak kernel only information.
+	 * As such refuse to use the feature if @current is not in the initial
+	 * PID namespace.
+	 */
+	if (task_active_pid_ns(current) != &init_pid_ns)
+		return -EINVAL;
+
+	/*
 	 * only implemented when ctxid tracing is enabled, i.e. at least one
 	 * ctxid comparator is implemented and ctxid is greater than 0 bits
 	 * in length
 	 */
 	if (!drvdata->ctxid_size || !drvdata->numcidc)
 		return -EINVAL;
-	if (kstrtoul(buf, 16, &vpid))
+	if (kstrtoul(buf, 16, &pid))
 		return -EINVAL;
 
-	pid = coresight_vpid_to_pid(vpid);
-
 	spin_lock(&drvdata->spinlock);
 	idx = config->ctxid_idx;
 	config->ctxid_pid[idx] = (u64)pid;
-	config->ctxid_vpid[idx] = (u64)vpid;
 	spin_unlock(&drvdata->spinlock);
 	return size;
 }

@@ -1682,6 +1697,13 @@ static ssize_t ctxid_masks_show(struct device *dev,
 	struct etmv4_drvdata *drvdata = dev_get_drvdata(dev->parent);
 	struct etmv4_config *config = &drvdata->config;
 
+	/*
+	 * Don't use contextID tracing if coming from a PID namespace.  See
+	 * comment in ctxid_pid_store().
+	 */
+	if (task_active_pid_ns(current) != &init_pid_ns)
+		return -EINVAL;
+
 	spin_lock(&drvdata->spinlock);
 	val1 = config->ctxid_mask0;
 	val2 = config->ctxid_mask1;

@@ -1699,6 +1721,13 @@ static ssize_t ctxid_masks_store(struct device *dev,
 	struct etmv4_config *config = &drvdata->config;
 
 	/*
+	 * Don't use contextID tracing if coming from a PID namespace.  See
+	 * comment in ctxid_pid_store().
+	 */
+	if (task_active_pid_ns(current) != &init_pid_ns)
+		return -EINVAL;
+
+	/*
 	 * only implemented when ctxid tracing is enabled, i.e. at least one
 	 * ctxid comparator is implemented and ctxid is greater than 0 bits
 	 * in length

index b7c4a6f6c6b9..52786e9d8926 100644
@@ -230,8 +230,6 @@
  * @addr_type:	Current status of the comparator register.
  * @ctxid_idx:	Context ID index selector.
  * @ctxid_pid:	Value of the context ID comparator.
- * @ctxid_vpid:	Virtual PID seen by users if PID namespace is enabled, otherwise
- *		the same value of ctxid_pid.
  * @ctxid_mask0:Context ID comparator mask for comparator 0-3.
  * @ctxid_mask1:Context ID comparator mask for comparator 4-7.
  * @vmid_idx:	VM ID index selector.

@@ -274,7 +272,6 @@ struct etmv4_config {
 	u8				addr_type[ETM_MAX_SINGLE_ADDR_CMP];
 	u8				ctxid_idx;
 	u64				ctxid_pid[ETMv4_MAX_CTXID_CMP];
-	u64				ctxid_vpid[ETMv4_MAX_CTXID_CMP];
 	u32				ctxid_mask0;
 	u32				ctxid_mask1;
 	u8				vmid_idx;

index c265e0468414..e5421b83e4e6 100644
@@ -267,24 +267,4 @@ static inline struct coresight_platform_data *of_get_coresight_platform_data(
 	struct device *dev, const struct device_node *node) { return NULL; }
 #endif
 
-#ifdef CONFIG_PID_NS
-static inline unsigned long
-coresight_vpid_to_pid(unsigned long vpid)
-{
-	struct task_struct *task = NULL;
-	unsigned long pid = 0;
-
-	rcu_read_lock();
-	task = find_task_by_vpid(vpid);
-	if (task)
-		pid = task_pid_nr(task);
-	rcu_read_unlock();
-
-	return pid;
-}
-#else
-static inline unsigned long
-coresight_vpid_to_pid(unsigned long vpid) { return vpid; }
-#endif
-
 #endif