audit: fix refcounting in audit-tree
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
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1 changed files with 2 additions and 3 deletions
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@ -250,7 +250,6 @@ static void untag_chunk(struct node *p)
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spin_unlock(&hash_lock);
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spin_unlock(&entry->lock);
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fsnotify_destroy_mark(entry);
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fsnotify_put_mark(entry);
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goto out;
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}
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@ -293,7 +292,6 @@ static void untag_chunk(struct node *p)
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spin_unlock(&hash_lock);
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spin_unlock(&entry->lock);
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fsnotify_destroy_mark(entry);
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fsnotify_put_mark(entry);
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goto out;
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Fallback:
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@ -332,6 +330,7 @@ static int create_chunk(struct inode *inode, struct audit_tree *tree)
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spin_unlock(&hash_lock);
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chunk->dead = 1;
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spin_unlock(&entry->lock);
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fsnotify_get_mark(entry);
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fsnotify_destroy_mark(entry);
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fsnotify_put_mark(entry);
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return 0;
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@ -412,6 +411,7 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree)
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spin_unlock(&chunk_entry->lock);
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spin_unlock(&old_entry->lock);
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fsnotify_get_mark(chunk_entry);
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fsnotify_destroy_mark(chunk_entry);
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fsnotify_put_mark(chunk_entry);
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@ -445,7 +445,6 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree)
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spin_unlock(&old_entry->lock);
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fsnotify_destroy_mark(old_entry);
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fsnotify_put_mark(old_entry); /* pair to fsnotify_find mark_entry */
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fsnotify_put_mark(old_entry); /* and kill it */
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return 0;
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}
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