linux-kernel - [PATCH 1/5] seccomp: Add find

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Date:   Sun, 24 May 2020 16:39:38 -0700
From:   Sargun Dhillon <sargun@...gun.me>
To:     linux-kernel@...r.kernel.org,
        containers@...ts.linux-foundation.org, linux-api@...r.kernel.org
Cc:     Sargun Dhillon <sargun@...gun.me>, christian.brauner@...ntu.com,
        tycho@...ho.ws, keescook@...omium.org, cyphar@...har.com,
        Jeffrey Vander Stoep <jeffv@...gle.com>, jannh@...gle.com,
        rsesek@...gle.com, palmer@...gle.com,
        Matt Denton <mpdenton@...gle.com>,
        Kees Cook <keescook@...gle.com>
Subject: [PATCH 1/5] seccomp: Add find_notification helper

This adds a helper which can iterate through a seccomp_filter to
find a notification matching an ID. It removes several replicated
chunks of code.

Signed-off-by: Sargun Dhillon <sargun@...gun.me>
Cc: Matt Denton <mpdenton@...gle.com>
Cc: Kees Cook <keescook@...gle.com>,
Cc: Jann Horn <jannh@...gle.com>,
Cc: Robert Sesek <rsesek@...gle.com>,
Cc: Chris Palmer <palmer@...gle.com>
Cc: Christian Brauner <christian.brauner@...ntu.com>
Cc: Tycho Andersen <tycho@...ho.ws>
---
 kernel/seccomp.c | 38 +++++++++++++++++++++-----------------
 1 file changed, 21 insertions(+), 17 deletions(-)

diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 55a6184f5990..f6ce94b7a167 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -1021,10 +1021,25 @@ static int seccomp_notify_release(struct inode *inode, struct file *file)
 	return 0;
 }
 
+/* must be called with notif_lock held */
+static inline struct seccomp_knotif *
+find_notification(struct seccomp_filter *filter, u64 id)
+{
+	struct seccomp_knotif *cur;
+
+	list_for_each_entry(cur, &filter->notif->notifications, list) {
+		if (cur->id == id)
+			return cur;
+	}
+
+	return NULL;
+}
+
+
 static long seccomp_notify_recv(struct seccomp_filter *filter,
 				void __user *buf)
 {
-	struct seccomp_knotif *knotif = NULL, *cur;
+	struct seccomp_knotif *knotif, *cur;
 	struct seccomp_notif unotif;
 	ssize_t ret;
 
@@ -1078,14 +1093,8 @@ static long seccomp_notify_recv(struct seccomp_filter *filter,
 		 * may have died when we released the lock, so we need to make
 		 * sure it's still around.
 		 */
-		knotif = NULL;
 		mutex_lock(&filter->notify_lock);
-		list_for_each_entry(cur, &filter->notif->notifications, list) {
-			if (cur->id == unotif.id) {
-				knotif = cur;
-				break;
-			}
-		}
+		knotif = find_notification(filter, unotif.id);
 
 		if (knotif) {
 			knotif->state = SECCOMP_NOTIFY_INIT;
@@ -1150,7 +1159,7 @@ static long seccomp_notify_send(struct seccomp_filter *filter,
 static long seccomp_notify_id_valid(struct seccomp_filter *filter,
 				    void __user *buf)
 {
-	struct seccomp_knotif *knotif = NULL;
+	struct seccomp_knotif *knotif;
 	u64 id;
 	long ret;
 
@@ -1162,15 +1171,10 @@ static long seccomp_notify_id_valid(struct seccomp_filter *filter,
 		return ret;
 
 	ret = -ENOENT;
-	list_for_each_entry(knotif, &filter->notif->notifications, list) {
-		if (knotif->id == id) {
-			if (knotif->state == SECCOMP_NOTIFY_SENT)
-				ret = 0;
-			goto out;
-		}
-	}
+	knotif = find_notification(filter, id);
+	if (knotif && knotif->state == SECCOMP_NOTIFY_SENT)
+		ret = 0;
 
-out:
 	mutex_unlock(&filter->notify_lock);
 	return ret;
 }
-- 
2.25.1