[PATCH] selinux: add selinux_status_get_seq() function

[PATCH] selinux: add selinux_status_get_seq() function

[Sebastien Buisson]

Add selinux_status_get_seq() function to give access to sequence
number of current SELinux policy loaded to the rest of the kernel.

Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
---
 include/linux/selinux.h      |  7 +++++++
 security/selinux/ss/status.c | 21 +++++++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/include/linux/selinux.h b/include/linux/selinux.h
index 44f4596..926f9f0 100644
--- a/include/linux/selinux.h
+++ b/include/linux/selinux.h
@@ -24,12 +24,19 @@
  * selinux_is_enabled - is SELinux enabled?
  */
 bool selinux_is_enabled(void);
+u32 selinux_status_get_seq(void);
 #else
 
 static inline bool selinux_is_enabled(void)
 {
 	return false;
 }
+
+static inline u32 selinux_status_get_seq(void)
+{
+	return 0;
+}
+
 #endif	/* CONFIG_SECURITY_SELINUX */
 
 #endif /* _LINUX_SELINUX_H */
diff --git a/security/selinux/ss/status.c b/security/selinux/ss/status.c
index d982365..a0670d3 100644
--- a/security/selinux/ss/status.c
+++ b/security/selinux/ss/status.c
@@ -124,3 +124,24 @@ void selinux_status_update_policyload(int seqno)
 	}
 	mutex_unlock(&selinux_status_lock);
 }
+
+/*
+ * selinux_status_get_seq
+ *
+ * It gets current sequence of policy loaded.
+ */
+u32 selinux_status_get_seq(void)
+{
+	struct selinux_kernel_status   *status;
+	u32				seq = 0;
+
+	mutex_lock(&selinux_status_lock);
+	if (selinux_status_page) {
+		status = page_address(selinux_status_page);
+		seq = status->sequence;
+	}
+	mutex_unlock(&selinux_status_lock);
+
+	return seq;
+}
+EXPORT_SYMBOL_GPL(selinux_status_get_seq);
-- 
1.8.3.1

Re: [PATCH] selinux: add selinux_status_get_seq() function

[Paul Moore]

On Wed, Apr 12, 2017 at 5:12 AM, Sebastien Buisson
<sbuisson.ddn@gmail.com> wrote:
> Add selinux_status_get_seq() function to give access to sequence
> number of current SELinux policy loaded to the rest of the kernel.
>
> Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
> ---
>  include/linux/selinux.h      |  7 +++++++
>  security/selinux/ss/status.c | 21 +++++++++++++++++++++
>  2 files changed, 28 insertions(+)

See my comments on your other patch, they apply here as well.

> diff --git a/include/linux/selinux.h b/include/linux/selinux.h
> index 44f4596..926f9f0 100644
> --- a/include/linux/selinux.h
> +++ b/include/linux/selinux.h
> @@ -24,12 +24,19 @@
>   * selinux_is_enabled - is SELinux enabled?
>   */
>  bool selinux_is_enabled(void);
> +u32 selinux_status_get_seq(void);
>  #else
>
>  static inline bool selinux_is_enabled(void)
>  {
>         return false;
>  }
> +
> +static inline u32 selinux_status_get_seq(void)
> +{
> +       return 0;
> +}
> +
>  #endif /* CONFIG_SECURITY_SELINUX */
>
>  #endif /* _LINUX_SELINUX_H */
> diff --git a/security/selinux/ss/status.c b/security/selinux/ss/status.c
> index d982365..a0670d3 100644
> --- a/security/selinux/ss/status.c
> +++ b/security/selinux/ss/status.c
> @@ -124,3 +124,24 @@ void selinux_status_update_policyload(int seqno)
>         }
>         mutex_unlock(&selinux_status_lock);
>  }
> +
> +/*
> + * selinux_status_get_seq
> + *
> + * It gets current sequence of policy loaded.
> + */
> +u32 selinux_status_get_seq(void)
> +{
> +       struct selinux_kernel_status   *status;
> +       u32                             seq = 0;
> +
> +       mutex_lock(&selinux_status_lock);
> +       if (selinux_status_page) {
> +               status = page_address(selinux_status_page);
> +               seq = status->sequence;
> +       }
> +       mutex_unlock(&selinux_status_lock);
> +
> +       return seq;
> +}
> +EXPORT_SYMBOL_GPL(selinux_status_get_seq);
> --
> 1.8.3.1
>
> --
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-- 
paul moore
security @ redhat

Re: [PATCH] selinux: add selinux_status_get_seq() function

[Stephen Smalley]

On Wed, 2017-04-12 at 18:12 +0900, Sebastien Buisson wrote:
> Add selinux_status_get_seq() function to give access to sequence
> number of current SELinux policy loaded to the rest of the kernel.
> 
> Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
> ---
>  include/linux/selinux.h      |  7 +++++++
>  security/selinux/ss/status.c | 21 +++++++++++++++++++++
>  2 files changed, 28 insertions(+)
> 
> diff --git a/include/linux/selinux.h b/include/linux/selinux.h
> index 44f4596..926f9f0 100644
> --- a/include/linux/selinux.h
> +++ b/include/linux/selinux.h
> @@ -24,12 +24,19 @@
>   * selinux_is_enabled - is SELinux enabled?
>   */
>  bool selinux_is_enabled(void);
> +u32 selinux_status_get_seq(void);
>  #else
>  
>  static inline bool selinux_is_enabled(void)
>  {
>  	return false;
>  }
> +
> +static inline u32 selinux_status_get_seq(void)
> +{
> +	return 0;
> +}
> +
>  #endif	/* CONFIG_SECURITY_SELINUX */
>  
>  #endif /* _LINUX_SELINUX_H */
> diff --git a/security/selinux/ss/status.c
> b/security/selinux/ss/status.c
> index d982365..a0670d3 100644
> --- a/security/selinux/ss/status.c
> +++ b/security/selinux/ss/status.c
> @@ -124,3 +124,24 @@ void selinux_status_update_policyload(int seqno)
>  	}
>  	mutex_unlock(&selinux_status_lock);
>  }
> +
> +/*
> + * selinux_status_get_seq
> + *
> + * It gets current sequence of policy loaded.
> + */
> +u32 selinux_status_get_seq(void)
> +{
> +	struct selinux_kernel_status   *status;
> +	u32				seq = 0;
> +
> +	mutex_lock(&selinux_status_lock);
> +	if (selinux_status_page) {
> +		status = page_address(selinux_status_page);
> +		seq = status->sequence;
> +	}
> +	mutex_unlock(&selinux_status_lock);
> +
> +	return seq;
> +}
> +EXPORT_SYMBOL_GPL(selinux_status_get_seq);

status->sequence is a sequence number for the seqlock logic, not the
policy sequence number.  You likely want avc_policy_seqno() instead,
although I can't tell without seeing the user of this function. 
Regardless, as with the other patch, there needs to be an in-tree user
and a LSM hook interface to use this outside of the SELinux code
itself.