From b707ddee11d1dc4518ab7f1aa5e7af9ceaa23317 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Sun, 31 May 2020 13:50:28 +0200 Subject: seccomp: rename "usage" to "refs" and document 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 Cc: Kees Cook Cc: Matt Denton Cc: Sargun Dhillon Cc: Jann Horn Cc: Chris Palmer Cc: Aleksa Sarai Cc: Robert Sesek Cc: Jeffrey Vander Stoep Cc: Linux Containers Signed-off-by: Christian Brauner Link: https://lore.kernel.org/r/20200531115031.391515-1-christian.brauner@ubuntu.com Signed-off-by: Kees Cook --- kernel/seccomp.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) (limited to 'kernel/seccomp.c') diff --git a/kernel/seccomp.c b/kernel/seccomp.c index e711d697afb6..d4dd3344e312 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -107,10 +107,11 @@ 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 @@ -125,10 +126,10 @@ 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; @@ -464,7 +465,7 @@ 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; } @@ -558,7 +559,7 @@ 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 */ @@ -581,7 +582,7 @@ 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); -- cgit