linux-kernel - [PATCH] apparmor: use per file locks for transactional queries

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Date:   Fri, 30 Jul 2021 01:23:55 -0400
From:   Hamza Mahfooz <someguy@...ective-light.com>
To:     linux-kernel@...r.kernel.org
Cc:     Hamza Mahfooz <someguy@...ective-light.com>,
        John Johansen <john.johansen@...onical.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        linux-security-module@...r.kernel.org
Subject: [PATCH] apparmor: use per file locks for transactional queries

As made mention of in commit 1dea3b41e84c5 ("apparmor: speed up
transactional queries"), a single lock is currently used to synchronize
transactional queries. We can, use the lock allocated for each file by
VFS instead.

Signed-off-by: Hamza Mahfooz <someguy@...ective-light.com>
---
 security/apparmor/apparmorfs.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/security/apparmor/apparmorfs.c b/security/apparmor/apparmorfs.c
index 2ee3b3d29f10..c0b626a271a0 100644
--- a/security/apparmor/apparmorfs.c
+++ b/security/apparmor/apparmorfs.c
@@ -812,8 +812,6 @@ struct multi_transaction {
 };
 
 #define MULTI_TRANSACTION_LIMIT (PAGE_SIZE - sizeof(struct multi_transaction))
-/* TODO: replace with per file lock */
-static DEFINE_SPINLOCK(multi_transaction_lock);
 
 static void multi_transaction_kref(struct kref *kref)
 {
@@ -847,10 +845,10 @@ static void multi_transaction_set(struct file *file,
 	AA_BUG(n > MULTI_TRANSACTION_LIMIT);
 
 	new->size = n;
-	spin_lock(&multi_transaction_lock);
+	spin_lock(&file->f_lock);
 	old = (struct multi_transaction *) file->private_data;
 	file->private_data = new;
-	spin_unlock(&multi_transaction_lock);
+	spin_unlock(&file->f_lock);
 	put_multi_transaction(old);
 }
 
@@ -879,9 +877,10 @@ static ssize_t multi_transaction_read(struct file *file, char __user *buf,
 	struct multi_transaction *t;
 	ssize_t ret;
 
-	spin_lock(&multi_transaction_lock);
+	spin_lock(&file->f_lock);
 	t = get_multi_transaction(file->private_data);
-	spin_unlock(&multi_transaction_lock);
+	spin_unlock(&file->f_lock);
+
 	if (!t)
 		return 0;
 
-- 
2.32.0