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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 02/10] audit: Fix possible spurious -ENOSPC error
Date: Tue, 10 Jul 2018 12:02:08 +0200	[thread overview]
Message-ID: <20180710100217.12866-3-jack@suse.cz> (raw)
In-Reply-To: <20180710100217.12866-1-jack@suse.cz>

When an inode is tagged with a tree, tag_chunk() checks whether there is
audit_tree_group mark attached to the inode and adds one if not. However
nothing protects another tag_chunk() to add the mark between we've
checked and try to add the fsnotify mark thus resulting in an error from
fsnotify_add_mark() and consequently an ENOSPC error from tag_chunk().

Fix the problem by holding mark_mutex over the whole check-insert code
sequence.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 kernel/audit_tree.c | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
index 1c82eb6674c4..de8d344d91b1 100644
--- a/kernel/audit_tree.c
+++ b/kernel/audit_tree.c
@@ -342,25 +342,29 @@ static void untag_chunk(struct node *p)
 	spin_lock(&hash_lock);
 }
 
+/* Call with group->mark_mutex held, releases it */
 static int create_chunk(struct inode *inode, struct audit_tree *tree)
 {
 	struct fsnotify_mark *entry;
 	struct audit_chunk *chunk = alloc_chunk(1);
-	if (!chunk)
+
+	if (!chunk) {
+		mutex_unlock(&audit_tree_group->mark_mutex);
 		return -ENOMEM;
+	}
 
 	entry = &chunk->mark;
-	if (fsnotify_add_inode_mark(entry, inode, 0)) {
+	if (fsnotify_add_inode_mark_locked(entry, inode, 0)) {
+		mutex_unlock(&audit_tree_group->mark_mutex);
 		fsnotify_put_mark(entry);
 		return -ENOSPC;
 	}
 
-	mutex_lock(&entry->group->mark_mutex);
 	spin_lock(&hash_lock);
 	if (tree->goner) {
 		spin_unlock(&hash_lock);
 		chunk->dead = 1;
-		mutex_unlock(&entry->group->mark_mutex);
+		mutex_unlock(&audit_tree_group->mark_mutex);
 		fsnotify_destroy_mark(entry, audit_tree_group);
 		fsnotify_put_mark(entry);
 		return 0;
@@ -375,7 +379,7 @@ static int create_chunk(struct inode *inode, struct audit_tree *tree)
 	}
 	insert_hash(chunk);
 	spin_unlock(&hash_lock);
-	mutex_unlock(&entry->group->mark_mutex);
+	mutex_unlock(&audit_tree_group->mark_mutex);
 	fsnotify_put_mark(entry);	/* drop initial reference */
 	return 0;
 }
@@ -389,6 +393,7 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree)
 	struct node *p;
 	int n;
 
+	mutex_lock(&audit_tree_group->mark_mutex);
 	old_entry = fsnotify_find_mark(&inode->i_fsnotify_marks,
 				       audit_tree_group);
 	if (!old_entry)
@@ -401,6 +406,7 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree)
 	for (n = 0; n < old->count; n++) {
 		if (old->owners[n].owner == tree) {
 			spin_unlock(&hash_lock);
+			mutex_unlock(&audit_tree_group->mark_mutex);
 			fsnotify_put_mark(old_entry);
 			return 0;
 		}
@@ -409,20 +415,20 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree)
 
 	chunk = alloc_chunk(old->count + 1);
 	if (!chunk) {
+		mutex_unlock(&audit_tree_group->mark_mutex);
 		fsnotify_put_mark(old_entry);
 		return -ENOMEM;
 	}
 
 	chunk_entry = &chunk->mark;
 
-	mutex_lock(&old_entry->group->mark_mutex);
 	/*
 	 * 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 */
-		mutex_unlock(&old_entry->group->mark_mutex);
+		mutex_unlock(&audit_tree_group->mark_mutex);
 		fsnotify_put_mark(old_entry);
 		fsnotify_put_mark(&chunk->mark);
 		return -ENOENT;
@@ -430,7 +436,7 @@ 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)) {
-		mutex_unlock(&old_entry->group->mark_mutex);
+		mutex_unlock(&audit_tree_group->mark_mutex);
 		fsnotify_put_mark(chunk_entry);
 		fsnotify_put_mark(old_entry);
 		return -ENOSPC;
@@ -440,7 +446,7 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree)
 	if (tree->goner) {
 		spin_unlock(&hash_lock);
 		chunk->dead = 1;
-		mutex_unlock(&old_entry->group->mark_mutex);
+		mutex_unlock(&audit_tree_group->mark_mutex);
 
 		fsnotify_destroy_mark(chunk_entry, audit_tree_group);
 
@@ -471,7 +477,7 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree)
 		list_add(&tree->same_root, &chunk->trees);
 	}
 	spin_unlock(&hash_lock);
-	mutex_unlock(&old_entry->group->mark_mutex);
+	mutex_unlock(&audit_tree_group->mark_mutex);
 	fsnotify_destroy_mark(old_entry, audit_tree_group);
 	fsnotify_put_mark(chunk_entry);	/* drop initial reference */
 	fsnotify_put_mark(old_entry); /* pair to fsnotify_find mark_entry */
-- 
2.16.4

  parent 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 ` [PATCH 01/10] audit_tree: Remove mark->lock locking Jan Kara
2018-07-27  4:47   ` Paul Moore
2018-09-04  9:53     ` Jan Kara
2018-07-10 10:02 ` Jan Kara [this message]
2018-07-27  4:47   ` [PATCH 02/10] audit: Fix possible spurious -ENOSPC error 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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