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[RFC,3/6] proc: add proc_splice_unmountable()

Message ID 20240806-work-procfs-v1-3-fb04e1d09f0c@kernel.org (mailing list archive)
State New
Headers show
Series proc: restrict overmounting of ephemeral entities | expand

Commit Message

Christian Brauner Aug. 6, 2024, 4:02 p.m. UTC 
Add a tiny procfs helper to splice a dentry that cannot be mounted upon.

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/proc/internal.h | 13 +++++++++++++
 1 file changed, 13 insertions(+)
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Patch

diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index a8a8576d8592..9e3f25e4c188 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -349,3 +349,16 @@  static inline void pde_force_lookup(struct proc_dir_entry *pde)
 	/* /proc/net/ entries can be changed under us by setns(CLONE_NEWNET) */
 	pde->proc_dops = &proc_net_dentry_ops;
 }
+
+/*
+ * Add a new procfs dentry that can't serve as a mountpoint. That should
+ * encompass anything that is ephemeral and can just disappear while the
+ * process is still around.
+ */
+static inline struct dentry *proc_splice_unmountable(struct inode *inode,
+		struct dentry *dentry, const struct dentry_operations *d_ops)
+{
+	d_set_d_op(dentry, d_ops);
+	dont_mount(dentry);
+	return d_splice_alias(inode, dentry);
+}