[Devel] [PATCH vz9 6/6] proc: block mounting on top of /proc/<pid>/fdinfo/*

[Vasileios Almpanis]

From: Christian Brauner <brauner at kernel.org>

Entries under /proc/<pid>/fdinfo/* are ephemeral and may go away before
the process dies. As such allowing them to be used as mount points
creates the ability to leak mounts that linger until the process dies
with no ability to unmount them until then. Don't allow using them as
mountpoints.

Link: https://lore.kernel.org/r/20240806-work-procfs-v1-6-fb04e1d09f0c@kernel.org
Reviewed-by: Josef Bacik <josef at toxicpanda.com>
Signed-off-by: Christian Brauner <brauner at kernel.org>
(cherry picked from commit 36272b209ccae52b181fd7594ff4ceffb32027c2)

https://virtuozzo.atlassian.net/browse/VSTOR-121919
Signed-off-by: Vasileios Almpanis <vasileios.almpanis at virtuozzo.com>
---
 fs/proc/fd.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/proc/fd.c b/fs/proc/fd.c
index 5d6252dbefd1..10c5bc71a9fc 100644
--- a/fs/proc/fd.c
+++ b/fs/proc/fd.c
@@ -332,8 +332,8 @@ static struct dentry *proc_fdinfo_instantiate(struct dentry *dentry,
 	inode->i_fop = &proc_fdinfo_file_operations;
 	tid_fd_update_inode(task, inode, 0);
 
-	d_set_d_op(dentry, &tid_fd_dentry_operations);
-	return d_splice_alias(inode, dentry);
+	return proc_splice_unmountable(inode, dentry,
+				       &tid_fd_dentry_operations);
 }
 
 static struct dentry *
-- 
2.43.0