On Tue, Jan 30, 2024 at 06:37:49PM -0800, Linus Torvalds wrote:

On Tue, 30 Jan 2024 at 17:12, Al Viro [off-list ref] wrote:

quoted

quoted

+ *
+ * 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...

We hold the ref to the ei in the very dentry that is doing d_revalidate().

What's to stop ->d_revalidate() from being called in parallel with
__dentry_kill()?