Re: [PATCH 6/6] eventfs: clean up dentry ops and add revalidate function
From: Al Viro <viro@zeniv.linux.org.uk>
Date: 2024-01-31 01:12:54
Also in:
lkml
On Tue, Jan 30, 2024 at 11:03:55AM -0800, Linus Torvalds wrote:
+void eventfs_d_release(struct dentry *dentry)
{
- struct eventfs_inode *ei;
-
- mutex_lock(&eventfs_mutex);
- ei = dentry->d_fsdata;
- if (ei) {
- dentry->d_fsdata = NULL;
- put_ei(ei);
- }
- mutex_unlock(&eventfs_mutex);
+ put_ei(dentry->d_fsdata);
}I'd rather pass ->d_fsdata to that sucker (or exposed put_ei(), for that matter).
quoted hunk ↗ jump to hunk
@@ -857,6 +847,5 @@ void eventfs_remove_events_dir(struct eventfs_inode *ei) * sticks around while the other ei->dentry are created * and destroyed dynamically. */ - simple_recursive_removal(dentry, NULL);
That also needs to move earlier in the series - bisect hazard.
+ * + * Note that d_revalidate is called potentially under RCU, + * so it can't take the eventfs mutex etc. It's fine - if + * we open a file just as it's marked dead, things will + * still work just fine, and just see the old stale case.
Looks like use after free, unless freeing ei is RCU-delayed...
+ return !(ei && ei->is_freed);