netdev - [PATCH net-next v6 05/11] seccomp: Split put_seccomp_filter() with put

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Message-Id: <20170328234650.19695-6-mic@digikod.net>
Date:   Wed, 29 Mar 2017 01:46:44 +0200
From:   Mickaël Salaün <mic@...ikod.net>
To:     linux-kernel@...r.kernel.org
Cc:     Mickaël Salaün <mic@...ikod.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Andy Lutomirski <luto@...capital.net>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Casey Schaufler <casey@...aufler-ca.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        David Drysdale <drysdale@...gle.com>,
        "David S . Miller" <davem@...emloft.net>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        James Morris <james.l.morris@...cle.com>,
        Jann Horn <jann@...jh.net>, Jonathan Corbet <corbet@....net>,
        Matthew Garrett <mjg59@...f.ucam.org>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Kees Cook <keescook@...omium.org>,
        Paul Moore <paul@...l-moore.com>,
        Sargun Dhillon <sargun@...gun.me>,
        "Serge E . Hallyn" <serge@...lyn.com>,
        Shuah Khan <shuah@...nel.org>, Tejun Heo <tj@...nel.org>,
        Thomas Graf <tgraf@...g.ch>, Will Drewry <wad@...omium.org>,
        kernel-hardening@...ts.openwall.com, linux-api@...r.kernel.org,
        linux-security-module@...r.kernel.org, netdev@...r.kernel.org
Subject: [PATCH net-next v6 05/11] seccomp: Split put_seccomp_filter() with put_seccomp()

The semantic is unchanged. This will be useful for the Landlock
integration with seccomp (next commit).

Signed-off-by: Mickaël Salaün <mic@...ikod.net>
Cc: Kees Cook <keescook@...omium.org>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Will Drewry <wad@...omium.org>
---
 include/linux/seccomp.h |  4 ++--
 kernel/fork.c           |  2 +-
 kernel/seccomp.c        | 18 +++++++++++++-----
 3 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h
index ecc296c137cd..e25aee2cdfc0 100644
--- a/include/linux/seccomp.h
+++ b/include/linux/seccomp.h
@@ -77,10 +77,10 @@ static inline int seccomp_mode(struct seccomp *s)
 #endif /* CONFIG_SECCOMP */
 
 #ifdef CONFIG_SECCOMP_FILTER
-extern void put_seccomp_filter(struct task_struct *tsk);
+extern void put_seccomp(struct task_struct *tsk);
 extern void get_seccomp_filter(struct task_struct *tsk);
 #else  /* CONFIG_SECCOMP_FILTER */
-static inline void put_seccomp_filter(struct task_struct *tsk)
+static inline void put_seccomp(struct task_struct *tsk)
 {
 	return;
 }
diff --git a/kernel/fork.c b/kernel/fork.c
index 6c463c80e93d..a27d8e67ce33 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -363,7 +363,7 @@ void free_task(struct task_struct *tsk)
 #endif
 	rt_mutex_debug_task_free(tsk);
 	ftrace_graph_exit_task(tsk);
-	put_seccomp_filter(tsk);
+	put_seccomp(tsk);
 	arch_release_task_struct(tsk);
 	if (tsk->flags & PF_KTHREAD)
 		free_kthread_struct(tsk);
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 65f61077ad50..326f79e32127 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -64,6 +64,8 @@ struct seccomp_filter {
 /* Limit any path through the tree to 256KB worth of instructions. */
 #define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter))
 
+static void put_seccomp_filter(struct seccomp_filter *filter);
+
 /*
  * Endianness is explicitly ignored and left for BPF program authors to manage
  * as per the specific architecture.
@@ -314,7 +316,7 @@ static inline void seccomp_sync_threads(void)
 		 * current's path will hold a reference.  (This also
 		 * allows a put before the assignment.)
 		 */
-		put_seccomp_filter(thread);
+		put_seccomp_filter(thread->seccomp.filter);
 		smp_store_release(&thread->seccomp.filter,
 				  caller->seccomp.filter);
 
@@ -476,10 +478,11 @@ static inline void seccomp_filter_free(struct seccomp_filter *filter)
 	}
 }
 
-/* put_seccomp_filter - decrements the ref count of tsk->seccomp.filter */
-void put_seccomp_filter(struct task_struct *tsk)
+/* put_seccomp_filter - decrements the ref count of a filter */
+static void put_seccomp_filter(struct seccomp_filter *filter)
 {
-	struct seccomp_filter *orig = tsk->seccomp.filter;
+	struct seccomp_filter *orig = filter;
+
 	/* Clean up single-reference branches iteratively. */
 	while (orig && atomic_dec_and_test(&orig->usage)) {
 		struct seccomp_filter *freeme = orig;
@@ -488,6 +491,11 @@ void put_seccomp_filter(struct task_struct *tsk)
 	}
 }
 
+void put_seccomp(struct task_struct *tsk)
+{
+	put_seccomp_filter(tsk->seccomp.filter);
+}
+
 static void seccomp_init_siginfo(siginfo_t *info, int syscall, int reason)
 {
 	memset(info, 0, sizeof(*info));
@@ -914,7 +922,7 @@ long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
 	if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog)))
 		ret = -EFAULT;
 
-	put_seccomp_filter(task);
+	put_seccomp_filter(task->seccomp.filter);
 	return ret;
 
 out:
-- 
2.11.0