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kernfs: Move dput() outside of the RCU section.

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Al Viro pointed out that dput() might sleep and must not be invoked
within an RCU section.

Keep only find_next_ancestor() winthin the RCU section.
Correct the wording in the comment.

Fixes: 6ef5b6fae3 ("kernfs: Drop kernfs_rwsem while invoking lookup_positive_unlocked().")
Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20250221084232.xksA_IQ4@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Sebastian Andrzej Siewior
2025-02-21 09:42:32 +01:00
committed by Greg Kroah-Hartman
parent e965efc4aa
commit c5020c5be9
1 changed files with 5 additions and 5 deletions
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fs/kernfs/mount.c
+5 -5
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@@ -222,17 +222,17 @@ struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
root = kernfs_root(kn);
/*
* As long as kn is valid, its parent can not vanish. This is cgroup's
* kn so it not have its parent replaced. Therefore it is safe to use
* kn so it can't have its parent replaced. Therefore it is safe to use
* the ancestor node outside of the RCU or locked section.
*/
if (WARN_ON_ONCE(!(root->flags & KERNFS_ROOT_INVARIANT_PARENT)))
return ERR_PTR(-EINVAL);
scoped_guard(rcu) {
knparent = find_next_ancestor(kn, NULL);
if (WARN_ON(!knparent)) {
dput(dentry);
return ERR_PTR(-EINVAL);
}
}
if (WARN_ON(!knparent)) {
dput(dentry);
return ERR_PTR(-EINVAL);
}
do {