linux-kernel - [PATCH 3.16 55/63] seccomp: extract check/assign mode helpers

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Date:   Sat, 22 Sep 2018 01:15:42 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Andy Lutomirski" <luto@...capital.net>,
        "Oleg Nesterov" <oleg@...hat.com>,
        "Kees Cook" <keescook@...omium.org>
Subject: [PATCH 3.16 55/63] seccomp: extract check/assign mode helpers

3.16.58-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Kees Cook <keescook@...omium.org>

commit 1f41b450416e689b9b7c8bfb750a98604f687a9b upstream.

To support splitting mode 1 from mode 2, extract the mode checking and
assignment logic into common functions.

Signed-off-by: Kees Cook <keescook@...omium.org>
Reviewed-by: Oleg Nesterov <oleg@...hat.com>
Reviewed-by: Andy Lutomirski <luto@...capital.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 kernel/seccomp.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -194,7 +194,23 @@ static u32 seccomp_run_filters(int sysca
 	}
 	return ret;
 }
+#endif /* CONFIG_SECCOMP_FILTER */
 
+static inline bool seccomp_may_assign_mode(unsigned long seccomp_mode)
+{
+	if (current->seccomp.mode && current->seccomp.mode != seccomp_mode)
+		return false;
+
+	return true;
+}
+
+static inline void seccomp_assign_mode(unsigned long seccomp_mode)
+{
+	current->seccomp.mode = seccomp_mode;
+	set_tsk_thread_flag(current, TIF_SECCOMP);
+}
+
+#ifdef CONFIG_SECCOMP_FILTER
 /**
  * seccomp_attach_filter: Attaches a seccomp filter to current.
  * @fprog: BPF program to install
@@ -490,8 +506,7 @@ static long seccomp_set_mode(unsigned lo
 {
 	long ret = -EINVAL;
 
-	if (current->seccomp.mode &&
-	    current->seccomp.mode != seccomp_mode)
+	if (!seccomp_may_assign_mode(seccomp_mode))
 		goto out;
 
 	switch (seccomp_mode) {
@@ -512,8 +527,7 @@ static long seccomp_set_mode(unsigned lo
 		goto out;
 	}
 
-	current->seccomp.mode = seccomp_mode;
-	set_thread_flag(TIF_SECCOMP);
+	seccomp_assign_mode(seccomp_mode);
 out:
 	return ret;
 }