[v3,1/4] seccomp: rename "usage" to "refs" and document

Submitted by Christian Brauner on May 31, 2020, 11:50 a.m.

Details

Message ID 20200531115031.391515-1-christian.brauner@ubuntu.com
State New
Series "Series without cover letter"
Headers show

Commit Message

Christian Brauner May 31, 2020, 11:50 a.m.
Naming the lifetime counter of a seccomp filter "usage" suggests a
little too strongly that its about tasks that are using this filter
while it also tracks other references such as the user notifier or
ptrace. This also updates the documentation to note this fact.

We'll be introducing an actual usage counter in a follow-up patch.

Cc: Tycho Andersen <tycho@tycho.ws>
Cc: Kees Cook <keescook@chromium.org>
Cc: Matt Denton <mpdenton@google.com>
Cc: Sargun Dhillon <sargun@sargun.me>
Cc: Jann Horn <jannh@google.com>
Cc: Chris Palmer <palmer@google.com>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Cc: Robert Sesek <rsesek@google.com>
Cc: Jeffrey Vander Stoep <jeffv@google.com>
Cc: Linux Containers <containers@lists.linux-foundation.org>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
/* v2 */
patch not present

/* v3 */
patch introduced
---
 kernel/seccomp.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)


base-commit: b9bbe6ed63b2b9f2c9ee5cbd0f2c946a2723f4ce

Patch hide | download patch | download mbox

diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 55a6184f5990..0ba2d6d0800f 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -106,10 +106,11 @@  struct notification {
 /**
  * struct seccomp_filter - container for seccomp BPF programs
  *
- * @usage: reference count to manage the object lifetime.
- *         get/put helpers should be used when accessing an instance
- *         outside of a lifetime-guarded section.  In general, this
- *         is only needed for handling filters shared across tasks.
+ * @refs: Reference count to manage the object lifetime.
+ *	  A filter's reference count is incremented for each directly
+ *	  attached task, once for the dependent filter, and if
+ *	  requested for the user notifier. When @refs reaches zero,
+ *	  the filter can be freed.
  * @log: true if all actions except for SECCOMP_RET_ALLOW should be logged
  * @prev: points to a previously installed, or inherited, filter
  * @prog: the BPF program to evaluate
@@ -124,10 +125,10 @@  struct notification {
  * how namespaces work.
  *
  * seccomp_filter objects should never be modified after being attached
- * to a task_struct (other than @usage).
+ * to a task_struct (other than @refs).
  */
 struct seccomp_filter {
-	refcount_t usage;
+	refcount_t refs;
 	bool log;
 	struct seccomp_filter *prev;
 	struct bpf_prog *prog;
@@ -461,7 +462,7 @@  static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog)
 		return ERR_PTR(ret);
 	}
 
-	refcount_set(&sfilter->usage, 1);
+	refcount_set(&sfilter->refs, 1);
 
 	return sfilter;
 }
@@ -554,7 +555,7 @@  static long seccomp_attach_filter(unsigned int flags,
 
 static void __get_seccomp_filter(struct seccomp_filter *filter)
 {
-	refcount_inc(&filter->usage);
+	refcount_inc(&filter->refs);
 }
 
 /* get_seccomp_filter - increments the reference count of the filter on @tsk */
@@ -577,7 +578,7 @@  static inline void seccomp_filter_free(struct seccomp_filter *filter)
 static void __put_seccomp_filter(struct seccomp_filter *orig)
 {
 	/* Clean up single-reference branches iteratively. */
-	while (orig && refcount_dec_and_test(&orig->usage)) {
+	while (orig && refcount_dec_and_test(&orig->refs)) {
 		struct seccomp_filter *freeme = orig;
 		orig = orig->prev;
 		seccomp_filter_free(freeme);

Comments

Kees Cook June 1, 2020, 6:33 p.m.
On Sun, May 31, 2020 at 01:50:28PM +0200, Christian Brauner wrote:
> Naming the lifetime counter of a seccomp filter "usage" suggests a
> little too strongly that its about tasks that are using this filter
> while it also tracks other references such as the user notifier or
> ptrace. This also updates the documentation to note this fact.
> 
> We'll be introducing an actual usage counter in a follow-up patch.
> 
> Cc: Tycho Andersen <tycho@tycho.ws>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Matt Denton <mpdenton@google.com>
> Cc: Sargun Dhillon <sargun@sargun.me>
> Cc: Jann Horn <jannh@google.com>
> Cc: Chris Palmer <palmer@google.com>
> Cc: Aleksa Sarai <cyphar@cyphar.com>
> Cc: Robert Sesek <rsesek@google.com>
> Cc: Jeffrey Vander Stoep <jeffv@google.com>
> Cc: Linux Containers <containers@lists.linux-foundation.org>
> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

Thanks! Applied to for-next/seccomp.