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pidfs: allow bind-mounts

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Allow bind-mounting pidfds. Similar to nsfs let's allow bind-mounts for
pidfds. This allows pidfds to be safely recovered and checked for
process recycling.

Link: https://lore.kernel.org/r/20241219-work-pidfs-mount-v1-1-dbc56198b839@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Christian Brauner 2024-12-19 18:01:32 +01:00
parent 16ecd47cb0
commit ef4144ac2d
No known key found for this signature in database
GPG key ID: 91C61BC06578DCA2
3 changed files with 10 additions and 3 deletions
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10
fs/namespace.c
View file

@ -32,6 +32,7 @@
#include <linux/fs_context.h>
#include <linux/shmem_fs.h>
#include <linux/mnt_idmapping.h>
#include <linux/pidfs.h>
#include <linux/nospec.h>
#include "pnode.h"
@ -2732,8 +2733,13 @@ static struct mount *__do_loopback(struct path *old_path, int recurse)
if (IS_MNT_UNBINDABLE(old))
return mnt;
if (!check_mnt(old) && old_path->dentry->d_op != &ns_dentry_operations)
return mnt;
if (!check_mnt(old)) {
const struct dentry_operations *d_op = old_path->dentry->d_op;
if (d_op != &ns_dentry_operations &&
d_op != &pidfs_dentry_operations)
return mnt;
}
if (!recurse && has_locked_children(old, old_path->dentry))
return mnt;

2
fs/pidfs.c
View file

@ -510,7 +510,7 @@ static char *pidfs_dname(struct dentry *dentry, char *buffer, int buflen)
return dynamic_dname(buffer, buflen, "anon_inode:[pidfd]");
}
static const struct dentry_operations pidfs_dentry_operations = {
const struct dentry_operations pidfs_dentry_operations = {
.d_delete = always_delete_dentry,
.d_dname = pidfs_dname,
.d_prune = stashed_dentry_prune,

1
include/linux/pidfs.h
View file

@ -6,5 +6,6 @@ struct file *pidfs_alloc_file(struct pid *pid, unsigned int flags);
void __init pidfs_init(void);
void pidfs_add_pid(struct pid *pid);
void pidfs_remove_pid(struct pid *pid);
extern const struct dentry_operations pidfs_dentry_operations;
#endif /* _LINUX_PID_FS_H */