Pidfd file handles are exhaustive meaning they don't require a handle on
another pidfd to pass to open_by_handle_at() so it can derive the
filesystem to decode in. Instead it can be derived from the file
handle itself. The same is possible for namespace file handles.
Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
---
fs/fhandle.c | 6 ++++++
fs/internal.h | 1 +
fs/nsfs.c | 10 ++++++++++
include/uapi/linux/fcntl.h | 1 +
4 files changed, 18 insertions(+)
diff --git a/fs/fhandle.c b/fs/fhandle.c
index 7c236f64cdea..f18c855bb0c2 100644
--- a/fs/fhandle.c
+++ b/fs/fhandle.c
@@ -11,6 +11,7 @@
#include <linux/personality.h>
#include <linux/uaccess.h>
#include <linux/compat.h>
+#include <linux/nsfs.h>
#include "internal.h"
#include "mount.h"
@@ -189,6 +190,11 @@ static int get_path_anchor(int fd, struct path *root)
return 0;
}
+ if (fd == FD_NSFS_ROOT) {
+ nsfs_get_root(root);
+ return 0;
+ }
+
return -EBADF;
}
diff --git a/fs/internal.h b/fs/internal.h
index 38e8aab27bbd..a33d18ee5b74 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -355,3 +355,4 @@ int anon_inode_getattr(struct mnt_idmap *idmap, const struct path *path,
int anon_inode_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
struct iattr *attr);
void pidfs_get_root(struct path *path);
+void nsfs_get_root(struct path *path);
diff --git a/fs/nsfs.c b/fs/nsfs.c
index a1585a2f4f03..3c6fcf652633 100644
--- a/fs/nsfs.c
+++ b/fs/nsfs.c
@@ -25,6 +25,14 @@
static struct vfsmount *nsfs_mnt;
+static struct path nsfs_root_path = {};
+
+void nsfs_get_root(struct path *path)
+{
+ *path = nsfs_root_path;
+ path_get(path);
+}
+
static long ns_ioctl(struct file *filp, unsigned int ioctl,
unsigned long arg);
static const struct file_operations ns_file_operations = {
@@ -616,4 +624,6 @@ void __init nsfs_init(void)
if (IS_ERR(nsfs_mnt))
panic("can't set nsfs up\n");
nsfs_mnt->mnt_sb->s_flags &= ~SB_NOUSER;
+ nsfs_root_path.mnt = nsfs_mnt;
+ nsfs_root_path.dentry = nsfs_mnt->mnt_root;
}
diff --git a/include/uapi/linux/fcntl.h b/include/uapi/linux/fcntl.h
index f291ab4f94eb..3741ea1b73d8 100644
--- a/include/uapi/linux/fcntl.h
+++ b/include/uapi/linux/fcntl.h
@@ -111,6 +111,7 @@
#define PIDFD_SELF_THREAD_GROUP -10001 /* Current thread group leader. */
#define FD_PIDFS_ROOT -10002 /* Root of the pidfs filesystem */
+#define FD_NSFS_ROOT -10003 /* Root of the nsfs filesystem */
#define FD_INVALID -10009 /* Invalid file descriptor: -10000 - EBADF = -10009 */
/* Generic flags for the *at(2) family of syscalls. */
--
2.47.3
