[PATCH v1 0/7] pid: Introduce helper task_is_in_root_ns()

[PATCH v1 0/7] pid: Introduce helper task_is_in_root_ns()

[Leo Yan]

The kernel uses open code to check if a process is in root PID namespace
or not in several places.

Suggested by Suzuki, this patch set is to create a helper function
task_is_in_root_ns() so we can use it replace open code.

To test this patch set, I built Arm64 kernel with enabling all relevant
modules, and verified the kernel with CoreSight module on Arm64 Juno
board.


Leo Yan (7):
  pid: Introduce helper task_is_in_root_ns()
  coresight: etm3x: Use task_is_in_root_ns() to check PID namespace
  coresight: etm4x: Use task_is_in_root_ns() to check PID namespace
  connector/cn_proc: Use task_is_in_root_ns() to check PID namespace
  coda: Use task_is_in_root_ns()
  audit: Use task_is_in_root_ns()
  taskstats: Use task_is_in_root_ns()

 drivers/connector/cn_proc.c                         | 2 +-
 drivers/hwtracing/coresight/coresight-etm3x-sysfs.c | 8 ++++----
 drivers/hwtracing/coresight/coresight-etm4x-sysfs.c | 8 ++++----
 fs/coda/inode.c                                     | 2 +-
 fs/coda/psdev.c                                     | 2 +-
 include/linux/pid_namespace.h                       | 5 +++++
 kernel/audit.c                                      | 2 +-
 kernel/taskstats.c                                  | 2 +-
 8 files changed, 18 insertions(+), 13 deletions(-)

-- 
2.25.1


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[PATCH v1 1/7] pid: Introduce helper task_is_in_root_ns()

[Leo Yan]

Currently the kernel uses open code in multiple places to check if a
task is in the root PID namespace with the kind of format:

  if (task_active_pid_ns(current) == &init_pid_ns)
      do_something();

This patch creates a new helper function, task_is_in_root_ns(), it
returns true if a passed task is in the root PID namespace, otherwise
returns false.  So it will be used to replace open codes.

Suggested-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Leo Yan <leo.yan@linaro.org>
---
 include/linux/pid_namespace.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
index 7c7e627503d2..bf82b373f022 100644
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h
@@ -86,4 +86,9 @@ extern struct pid_namespace *task_active_pid_ns(struct task_struct *tsk);
 void pidhash_init(void);
 void pid_idr_init(void);
 
+static inline bool task_is_in_root_ns(struct task_struct *tsk)
+{
+	return task_active_pid_ns(tsk) == &init_pid_ns;
+}
+
 #endif /* _LINUX_PID_NS_H */
-- 
2.25.1


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Re: [PATCH v1 1/7] pid: Introduce helper task_is_in_root_ns()

[Leon Romanovsky]

On Sun, Dec 05, 2021 at 10:50:59PM +0800, Leo Yan wrote:
> Currently the kernel uses open code in multiple places to check if a
> task is in the root PID namespace with the kind of format:
> 
>   if (task_active_pid_ns(current) == &init_pid_ns)
>       do_something();
> 
> This patch creates a new helper function, task_is_in_root_ns(), it
> returns true if a passed task is in the root PID namespace, otherwise
> returns false.  So it will be used to replace open codes.
> 
> Suggested-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> Signed-off-by: Leo Yan <leo.yan@linaro.org>
> ---
>  include/linux/pid_namespace.h | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
> index 7c7e627503d2..bf82b373f022 100644
> --- a/include/linux/pid_namespace.h
> +++ b/include/linux/pid_namespace.h
> @@ -86,4 +86,9 @@ extern struct pid_namespace *task_active_pid_ns(struct task_struct *tsk);
>  void pidhash_init(void);
>  void pid_idr_init(void);
>  
> +static inline bool task_is_in_root_ns(struct task_struct *tsk)

It is bad that this name doesn't reflect PID nature of this namespace.
Won't it better to name it task_is_in_init_pid_ns()?

Thanks

> +{
> +	return task_active_pid_ns(tsk) == &init_pid_ns;
> +}
> +
>  #endif /* _LINUX_PID_NS_H */
> -- 
> 2.25.1
> 

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Re: [PATCH v1 1/7] pid: Introduce helper task_is_in_root_ns()

[Leo Yan]

Hi Leon,

On Mon, Dec 06, 2021 at 08:49:01AM +0200, Leon Romanovsky wrote:
> On Sun, Dec 05, 2021 at 10:50:59PM +0800, Leo Yan wrote:

[...]

> > +static inline bool task_is_in_root_ns(struct task_struct *tsk)
> 
> It is bad that this name doesn't reflect PID nature of this namespace.
> Won't it better to name it task_is_in_init_pid_ns()?

Yes, task_is_in_init_pid_ns() is more clear.

Will respin for this.  Thank you for suggestion!

Leo

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Re: [PATCH v1 1/7] pid: Introduce helper task_is_in_root_ns()

[Leon Romanovsky]

On Mon, Dec 06, 2021 at 03:03:58PM +0800, Leo Yan wrote:
> Hi Leon,
> 
> On Mon, Dec 06, 2021 at 08:49:01AM +0200, Leon Romanovsky wrote:
> > On Sun, Dec 05, 2021 at 10:50:59PM +0800, Leo Yan wrote:
> 
> [...]
> 
> > > +static inline bool task_is_in_root_ns(struct task_struct *tsk)
> > 
> > It is bad that this name doesn't reflect PID nature of this namespace.
> > Won't it better to name it task_is_in_init_pid_ns()?
> 
> Yes, task_is_in_init_pid_ns() is more clear.
> 
> Will respin for this.  Thank you for suggestion!

Thanks

> 
> Leo

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[PATCH v1 2/7] coresight: etm3x: Use task_is_in_root_ns() to check PID namespace

[Leo Yan]

This patch uses helper task_is_in_root_ns() to replace open code for
checking if a task is in root PID namespace.

Signed-off-by: Leo Yan <leo.yan@linaro.org>
---
 drivers/hwtracing/coresight/coresight-etm3x-sysfs.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c b/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c
index e8c7649f123e..baba16ad9bb1 100644
--- a/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c
+++ b/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c
@@ -1030,7 +1030,7 @@ static ssize_t ctxid_pid_show(struct device *dev,
 	 * 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)
+	if (!task_is_in_root_ns(current))
 		return -EINVAL;
 
 	spin_lock(&drvdata->spinlock);
@@ -1058,7 +1058,7 @@ static ssize_t ctxid_pid_store(struct device *dev,
 	 * 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)
+	if (!task_is_in_root_ns(current))
 		return -EINVAL;
 
 	ret = kstrtoul(buf, 16, &pid);
@@ -1084,7 +1084,7 @@ static ssize_t ctxid_mask_show(struct device *dev,
 	 * 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)
+	if (!task_is_in_root_ns(current))
 		return -EINVAL;
 
 	val = config->ctxid_mask;
@@ -1104,7 +1104,7 @@ static ssize_t ctxid_mask_store(struct device *dev,
 	 * 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)
+	if (!task_is_in_root_ns(current))
 		return -EINVAL;
 
 	ret = kstrtoul(buf, 16, &val);
-- 
2.25.1


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[PATCH v1 3/7] coresight: etm4x: Use task_is_in_root_ns() to check PID namespace

[Leo Yan]

To avoid open code, this patch uses the helper task_is_in_root_ns() to
check if a task is in root PID namespace.

Signed-off-by: Leo Yan <leo.yan@linaro.org>
---
 drivers/hwtracing/coresight/coresight-etm4x-sysfs.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
index a0640fa5c55b..cd87ad8456d7 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
@@ -1890,7 +1890,7 @@ static ssize_t ctxid_pid_show(struct device *dev,
 	 * 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)
+	if (!task_is_in_root_ns(current))
 		return -EINVAL;
 
 	spin_lock(&drvdata->spinlock);
@@ -1918,7 +1918,7 @@ static ssize_t ctxid_pid_store(struct device *dev,
 	 * 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)
+	if (!task_is_in_root_ns(current))
 		return -EINVAL;
 
 	/*
@@ -1951,7 +1951,7 @@ static ssize_t ctxid_masks_show(struct device *dev,
 	 * 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)
+	if (!task_is_in_root_ns(current))
 		return -EINVAL;
 
 	spin_lock(&drvdata->spinlock);
@@ -1975,7 +1975,7 @@ static ssize_t ctxid_masks_store(struct device *dev,
 	 * 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)
+	if (!task_is_in_root_ns(current))
 		return -EINVAL;
 
 	/*
-- 
2.25.1


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[PATCH v1 4/7] connector/cn_proc: Use task_is_in_root_ns() to check PID namespace

[Leo Yan]

To avoid open code, this patch uses the helper task_is_in_root_ns() to
check if task is in root PID namespace.

Signed-off-by: Leo Yan <leo.yan@linaro.org>
---
 drivers/connector/cn_proc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/connector/cn_proc.c b/drivers/connector/cn_proc.c
index 646ad385e490..b8a4fa366b28 100644
--- a/drivers/connector/cn_proc.c
+++ b/drivers/connector/cn_proc.c
@@ -358,7 +358,7 @@ static void cn_proc_mcast_ctl(struct cn_msg *msg,
 	 * other namespaces.
 	 */
 	if ((current_user_ns() != &init_user_ns) ||
-	    (task_active_pid_ns(current) != &init_pid_ns))
+	    !task_is_in_root_ns(current))
 		return;
 
 	/* Can only change if privileged. */
-- 
2.25.1


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[PATCH v1 5/7] coda: Use task_is_in_root_ns()

[Leo Yan]

Replace open coded checking root PID namespace with
task_is_in_root_ns().

Signed-off-by: Leo Yan <leo.yan@linaro.org>
---
 fs/coda/inode.c | 2 +-
 fs/coda/psdev.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/coda/inode.c b/fs/coda/inode.c
index d9f1bd7153df..a7d630ac522e 100644
--- a/fs/coda/inode.c
+++ b/fs/coda/inode.c
@@ -152,7 +152,7 @@ static int coda_fill_super(struct super_block *sb, void *data, int silent)
 	int error;
 	int idx;
 
-	if (task_active_pid_ns(current) != &init_pid_ns)
+	if (!task_is_in_root_ns(current))
 		return -EINVAL;
 
 	idx = get_device_index((struct coda_mount_data *) data);
diff --git a/fs/coda/psdev.c b/fs/coda/psdev.c
index b39580ad4ce5..54db13bf2e06 100644
--- a/fs/coda/psdev.c
+++ b/fs/coda/psdev.c
@@ -270,7 +270,7 @@ static int coda_psdev_open(struct inode * inode, struct file * file)
 	struct venus_comm *vcp;
 	int idx, err;
 
-	if (task_active_pid_ns(current) != &init_pid_ns)
+	if (!task_is_in_root_ns(current))
 		return -EINVAL;
 
 	if (current_user_ns() != &init_user_ns)
-- 
2.25.1


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[PATCH v1 6/7] audit: Use task_is_in_root_ns()

[Leo Yan]

Replace open coded checking root PID namespace with
task_is_in_root_ns().

Signed-off-by: Leo Yan <leo.yan@linaro.org>
---
 kernel/audit.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/audit.c b/kernel/audit.c
index 121d37e700a6..c71d4182c05d 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -1034,7 +1034,7 @@ static int audit_netlink_ok(struct sk_buff *skb, u16 msg_type)
 	case AUDIT_MAKE_EQUIV:
 		/* Only support auditd and auditctl in initial pid namespace
 		 * for now. */
-		if (task_active_pid_ns(current) != &init_pid_ns)
+		if (!task_is_in_root_ns(current))
 			return -EPERM;
 
 		if (!netlink_capable(skb, CAP_AUDIT_CONTROL))
-- 
2.25.1


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[PATCH v1 7/7] taskstats: Use task_is_in_root_ns()

[Leo Yan]

Replace open coded checking root PID namespace with
task_is_in_root_ns().

Signed-off-by: Leo Yan <leo.yan@linaro.org>
---
 kernel/taskstats.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/taskstats.c b/kernel/taskstats.c
index 2b4898b4752e..c6a19d3911b3 100644
--- a/kernel/taskstats.c
+++ b/kernel/taskstats.c
@@ -284,7 +284,7 @@ static int add_del_listener(pid_t pid, const struct cpumask *mask, int isadd)
 	if (current_user_ns() != &init_user_ns)
 		return -EINVAL;
 
-	if (task_active_pid_ns(current) != &init_pid_ns)
+	if (!task_is_in_root_ns(current))
 		return -EINVAL;
 
 	if (isadd == REGISTER) {
-- 
2.25.1


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