On Wed, Sep 10, 2025 at 4:39 PM Christian Brauner brauner@kernel.org wrote:
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@kernel.org
Reviewed-by: Amir Goldstein amir73il@gmail.com
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