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[RFC,4/6] proc: block mounting on top of /proc/<pid>/map_files/*

Message ID 20240806-work-procfs-v1-4-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
Entries under /proc/<pid>/map_files/* 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.

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/proc/base.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
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Patch

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 72a1acd03675..fce3d377b826 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2276,8 +2276,8 @@  proc_map_files_instantiate(struct dentry *dentry,
 	inode->i_op = &proc_map_files_link_inode_operations;
 	inode->i_size = 64;
 
-	d_set_d_op(dentry, &tid_map_files_dentry_operations);
-	return d_splice_alias(inode, dentry);
+	return proc_splice_unmountable(inode, dentry,
+				       &tid_map_files_dentry_operations);
 }
 
 static struct dentry *proc_map_files_lookup(struct inode *dir,