audit: fix refcounting in audit-tree (a2140fc0) · Commits · 戴 / test

Refcounting of fsnotify_mark in audit tree is broken. E.g: refcount create_chunk alloc_chunk 1 fsnotify_add_mark 2 untag_chunk fsnotify_get_mark 3 fsnotify_destroy_mark audit_tree_freeing_mark 2 fsnotify_put_mark 1 fsnotify_put_mark 0 via destroy_list fsnotify_mark_destroy -1 This was reported by various people as triggering Oops when stopping auditd. We could just remove the put_mark from audit_tree_freeing_mark() but that would break freeing via inode destruction. So this patch simply omits a put_mark after calling destroy_mark or adds a get_mark before. The additional get_mark is necessary where there's no other put_mark after fsnotify_destroy_mark() since it assumes that the caller is holding a reference (or the inode is keeping the mark pinned, not the case here AFAICS). Signed-off-by:

Miklos Szeredi <mszeredi@suse.cz> Reported-by:

Valentin Avram <aval13@gmail.com> Reported-by:

Peter Moody <pmoody@google.com> Acked-by:

Eric Paris <eparis@redhat.com> CC: stable@vger.kernel.org

kernel/audit_tree.c

+2 −3

Original line number	Diff line number	Diff line
		@@ -250,7 +250,6 @@ static void untag_chunk(struct node *p)
		spin_unlock(&hash_lock);
		spin_unlock(&entry->lock);
		fsnotify_destroy_mark(entry);
		fsnotify_put_mark(entry);
		goto out;
		}

		@@ -293,7 +292,6 @@ static void untag_chunk(struct node *p)
		spin_unlock(&hash_lock);
		spin_unlock(&entry->lock);
		fsnotify_destroy_mark(entry);
		fsnotify_put_mark(entry);
		goto out;

		Fallback:
		@@ -332,6 +330,7 @@ static int create_chunk(struct inode inode, struct audit_tree tree)
		spin_unlock(&hash_lock);
		chunk->dead = 1;
		spin_unlock(&entry->lock);
		fsnotify_get_mark(entry);
		fsnotify_destroy_mark(entry);
		fsnotify_put_mark(entry);
		return 0;
		@@ -412,6 +411,7 @@ static int tag_chunk(struct inode inode, struct audit_tree tree)
		spin_unlock(&chunk_entry->lock);
		spin_unlock(&old_entry->lock);

		fsnotify_get_mark(chunk_entry);
		fsnotify_destroy_mark(chunk_entry);

		fsnotify_put_mark(chunk_entry);
		@@ -445,7 +445,6 @@ static int tag_chunk(struct inode inode, struct audit_tree tree)
		spin_unlock(&old_entry->lock);
		fsnotify_destroy_mark(old_entry);
		fsnotify_put_mark(old_entry); /* pair to fsnotify_find mark_entry */
		fsnotify_put_mark(old_entry); /* and kill it */
		return 0;
		}

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