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From: Jan Kara <jack@suse.cz>
To: linux-audit@redhat.com
Cc: Paul Moore <paul@paul-moore.com>, <linux-fsdevel@vger.kernel.org>,
	Al Viro <viro@ZenIV.linux.org.uk>,
	Richard Guy Briggs <rgb@redhat.com>,
	Amir Goldstein <amir73il@gmail.com>, Jan Kara <jack@suse.cz>
Subject: [PATCH 01/10] audit_tree: Remove mark->lock locking
Date: Tue, 10 Jul 2018 12:02:07 +0200	[thread overview]
Message-ID: <20180710100217.12866-2-jack@suse.cz> (raw)
In-Reply-To: <20180710100217.12866-1-jack@suse.cz>

Currently, audit_tree code uses mark->lock to protect against detaching
of mark from an inode. In most places it however also uses
mark->group->mark_mutex (as we need to atomically replace attached
marks) and this provides protection against mark detaching as well. So
just remove protection with mark->lock from audit tree code and replace
it with mark->group->mark_mutex protection in all the places. It
simplifies the code and gets rid of some ugly catches like calling
fsnotify_add_mark_locked() with mark->lock held (which cannot sleep only
because we hold a reference to another mark attached to the same inode).

Signed-off-by: Jan Kara <jack@suse.cz>
---
 kernel/audit_tree.c | 24 ++++--------------------
 1 file changed, 4 insertions(+), 20 deletions(-)

diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
index 02feef939560..1c82eb6674c4 100644
--- a/kernel/audit_tree.c
+++ b/kernel/audit_tree.c
@@ -193,7 +193,7 @@ static inline struct list_head *chunk_hash(unsigned long key)
 	return chunk_hash_heads + n % HASH_SIZE;
 }
 
-/* hash_lock & entry->lock is held by caller */
+/* hash_lock & entry->group->mark_mutex is held by caller */
 static void insert_hash(struct audit_chunk *chunk)
 {
 	unsigned long key = chunk_to_key(chunk);
@@ -256,13 +256,11 @@ static void untag_chunk(struct node *p)
 		new = alloc_chunk(size);
 
 	mutex_lock(&entry->group->mark_mutex);
-	spin_lock(&entry->lock);
 	/*
 	 * mark_mutex protects mark from getting detached and thus also from
 	 * mark->connector->obj getting NULL.
 	 */
 	if (chunk->dead || !(entry->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) {
-		spin_unlock(&entry->lock);
 		mutex_unlock(&entry->group->mark_mutex);
 		if (new)
 			fsnotify_put_mark(&new->mark);
@@ -280,7 +278,6 @@ static void untag_chunk(struct node *p)
 		list_del_init(&p->list);
 		list_del_rcu(&chunk->hash);
 		spin_unlock(&hash_lock);
-		spin_unlock(&entry->lock);
 		mutex_unlock(&entry->group->mark_mutex);
 		fsnotify_destroy_mark(entry, audit_tree_group);
 		goto out;
@@ -323,7 +320,6 @@ static void untag_chunk(struct node *p)
 	list_for_each_entry(owner, &new->trees, same_root)
 		owner->root = new;
 	spin_unlock(&hash_lock);
-	spin_unlock(&entry->lock);
 	mutex_unlock(&entry->group->mark_mutex);
 	fsnotify_destroy_mark(entry, audit_tree_group);
 	fsnotify_put_mark(&new->mark);	/* drop initial reference */
@@ -340,7 +336,6 @@ static void untag_chunk(struct node *p)
 	p->owner = NULL;
 	put_tree(owner);
 	spin_unlock(&hash_lock);
-	spin_unlock(&entry->lock);
 	mutex_unlock(&entry->group->mark_mutex);
 out:
 	fsnotify_put_mark(entry);
@@ -360,12 +355,12 @@ static int create_chunk(struct inode *inode, struct audit_tree *tree)
 		return -ENOSPC;
 	}
 
-	spin_lock(&entry->lock);
+	mutex_lock(&entry->group->mark_mutex);
 	spin_lock(&hash_lock);
 	if (tree->goner) {
 		spin_unlock(&hash_lock);
 		chunk->dead = 1;
-		spin_unlock(&entry->lock);
+		mutex_unlock(&entry->group->mark_mutex);
 		fsnotify_destroy_mark(entry, audit_tree_group);
 		fsnotify_put_mark(entry);
 		return 0;
@@ -380,7 +375,7 @@ static int create_chunk(struct inode *inode, struct audit_tree *tree)
 	}
 	insert_hash(chunk);
 	spin_unlock(&hash_lock);
-	spin_unlock(&entry->lock);
+	mutex_unlock(&entry->group->mark_mutex);
 	fsnotify_put_mark(entry);	/* drop initial reference */
 	return 0;
 }
@@ -421,14 +416,12 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree)
 	chunk_entry = &chunk->mark;
 
 	mutex_lock(&old_entry->group->mark_mutex);
-	spin_lock(&old_entry->lock);
 	/*
 	 * mark_mutex protects mark from getting detached and thus also from
 	 * mark->connector->obj getting NULL.
 	 */
 	if (!(old_entry->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) {
 		/* old_entry is being shot, lets just lie */
-		spin_unlock(&old_entry->lock);
 		mutex_unlock(&old_entry->group->mark_mutex);
 		fsnotify_put_mark(old_entry);
 		fsnotify_put_mark(&chunk->mark);
@@ -437,23 +430,16 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree)
 
 	if (fsnotify_add_mark_locked(chunk_entry, old_entry->connector->obj,
 				     FSNOTIFY_OBJ_TYPE_INODE, 1)) {
-		spin_unlock(&old_entry->lock);
 		mutex_unlock(&old_entry->group->mark_mutex);
 		fsnotify_put_mark(chunk_entry);
 		fsnotify_put_mark(old_entry);
 		return -ENOSPC;
 	}
 
-	/* even though we hold old_entry->lock, this is safe since chunk_entry->lock could NEVER have been grabbed before */
-	spin_lock(&chunk_entry->lock);
 	spin_lock(&hash_lock);
-
-	/* we now hold old_entry->lock, chunk_entry->lock, and hash_lock */
 	if (tree->goner) {
 		spin_unlock(&hash_lock);
 		chunk->dead = 1;
-		spin_unlock(&chunk_entry->lock);
-		spin_unlock(&old_entry->lock);
 		mutex_unlock(&old_entry->group->mark_mutex);
 
 		fsnotify_destroy_mark(chunk_entry, audit_tree_group);
@@ -485,8 +471,6 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree)
 		list_add(&tree->same_root, &chunk->trees);
 	}
 	spin_unlock(&hash_lock);
-	spin_unlock(&chunk_entry->lock);
-	spin_unlock(&old_entry->lock);
 	mutex_unlock(&old_entry->group->mark_mutex);
 	fsnotify_destroy_mark(old_entry, audit_tree_group);
 	fsnotify_put_mark(chunk_entry);	/* drop initial reference */
-- 
2.16.4

  reply	other threads:[~2018-07-10 10:02 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-10 10:02 [PATCH 0/10 v2] audit: Fix various races when tagging and untagging mounts Jan Kara
2018-07-10 10:02 ` Jan Kara [this message]
2018-07-27  4:47   ` [PATCH 01/10] audit_tree: Remove mark->lock locking Paul Moore
2018-09-04  9:53     ` Jan Kara
2018-07-10 10:02 ` [PATCH 02/10] audit: Fix possible spurious -ENOSPC error Jan Kara
2018-07-27  4:47   ` Paul Moore
2018-09-04 10:00     ` Jan Kara
2018-07-10 10:02 ` [PATCH 03/10] audit: Fix possible tagging failures Jan Kara
2018-07-10 10:02 ` [PATCH 04/10] audit: Embed key into chunk Jan Kara
2018-07-27  4:47   ` Paul Moore
2018-07-10 10:02 ` [PATCH 05/10] audit: Make hash table insertion safe against concurrent lookups Jan Kara
2018-07-10 10:02 ` [PATCH 06/10] audit: Factor out chunk replacement code Jan Kara
2018-07-11  7:58   ` Amir Goldstein
2018-07-11  8:26     ` Jan Kara
2018-07-11  9:01       ` Amir Goldstein
2018-07-11  9:23         ` Jan Kara
2018-07-27  4:47   ` Paul Moore
2018-07-10 10:02 ` [PATCH 07/10] audit: Remove pointless check in insert_hash() Jan Kara
2018-07-27  4:47   ` Paul Moore
2018-07-10 10:02 ` [PATCH 08/10] audit: Provide helper for dropping mark's chunk reference Jan Kara
2018-07-10 10:02 ` [PATCH 09/10] audit: Allocate fsnotify mark independently of chunk Jan Kara
2018-07-11  8:57   ` Amir Goldstein
2018-07-11 10:48     ` Amir Goldstein
2018-07-16 15:13       ` Jan Kara
2018-07-27  4:47   ` Paul Moore
2018-09-04 14:03     ` Jan Kara
2018-09-04 14:07       ` Jan Kara
2018-07-10 10:02 ` [PATCH 10/10] audit: Replace chunk attached to mark instead of replacing mark Jan Kara
2018-07-11 14:17   ` Amir Goldstein
2018-07-27  4:47   ` Paul Moore
2018-09-04 14:11     ` Jan Kara
2018-07-10 10:02 ` [PATCH 11/10 TESTSUITE] audit_testsuite: Add stress test for tree watches Jan Kara

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