On 2025-09-10, Christian Brauner brauner@kernel.org wrote:
The mount namespace has supported id retrieval for a while already. Add support for the other types as well.
Signed-off-by: Christian Brauner brauner@kernel.org
fs/nsfs.c | 74 +++++++++++++++++++++++++++++++++++++++-------- include/uapi/linux/nsfs.h | 12 ++++++-- 2 files changed, 72 insertions(+), 14 deletions(-)
diff --git a/fs/nsfs.c b/fs/nsfs.c index 3c6fcf652633..527480e67fd1 100644 --- a/fs/nsfs.c +++ b/fs/nsfs.c @@ -173,6 +173,13 @@ static bool nsfs_ioctl_valid(unsigned int cmd) case NS_GET_NSTYPE: case NS_GET_OWNER_UID: case NS_GET_MNTNS_ID:
- case NS_GET_NETNS_ID:
- case NS_GET_CGROUPNS_ID:
- case NS_GET_IPCNS_ID:
- case NS_GET_UTSNS_ID:
- case NS_GET_PIDNS_ID:
- case NS_GET_TIMENS_ID:
- case NS_GET_USERNS_ID: case NS_GET_PID_FROM_PIDNS: case NS_GET_TGID_FROM_PIDNS: case NS_GET_PID_IN_PIDNS:
@@ -226,18 +233,6 @@ static long ns_ioctl(struct file *filp, unsigned int ioctl, argp = (uid_t __user *) arg; uid = from_kuid_munged(current_user_ns(), user_ns->owner); return put_user(uid, argp);
- case NS_GET_MNTNS_ID: {
__u64 __user *idp;__u64 id;if (ns->ops->type != CLONE_NEWNS)return -EINVAL;mnt_ns = container_of(ns, struct mnt_namespace, ns);idp = (__u64 __user *)arg;id = mnt_ns->ns.ns_id;return put_user(id, idp);- } case NS_GET_PID_FROM_PIDNS: fallthrough; case NS_GET_TGID_FROM_PIDNS:
@@ -283,6 +278,61 @@ static long ns_ioctl(struct file *filp, unsigned int ioctl, ret = -ESRCH; return ret; }
- case NS_GET_MNTNS_ID:
fallthrough;- case NS_GET_NETNS_ID:
fallthrough;- case NS_GET_CGROUPNS_ID:
fallthrough;- case NS_GET_IPCNS_ID:
fallthrough;- case NS_GET_UTSNS_ID:
fallthrough;- case NS_GET_PIDNS_ID:
fallthrough;- case NS_GET_TIMENS_ID:
fallthrough;- case NS_GET_USERNS_ID: {
__u64 __user *idp;__u64 id;int expected_type;switch (ioctl) {case NS_GET_MNTNS_ID:expected_type = CLONE_NEWNS;break;case NS_GET_NETNS_ID:expected_type = CLONE_NEWNET;break;case NS_GET_CGROUPNS_ID:expected_type = CLONE_NEWCGROUP;break;case NS_GET_IPCNS_ID:expected_type = CLONE_NEWIPC;break;case NS_GET_UTSNS_ID:expected_type = CLONE_NEWUTS;break;case NS_GET_PIDNS_ID:expected_type = CLONE_NEWPID;break;case NS_GET_TIMENS_ID:expected_type = CLONE_NEWTIME;break;case NS_GET_USERNS_ID:expected_type = CLONE_NEWUSER;break;default:return -EINVAL;}if (ns->ops->type != expected_type)return -EINVAL;
While I get that having this be per-ns-type lets programs avoid being tricked into thinking that one namespace ID is actually another namespace, it feels a bit ugly to have to add a new ioctl for every new namespace.
If we added a way to get the CLONE_* flag for a namespace (NS_GET_TYPE) we could have just NS_GET_ID. Of course, we would have to trust userspace to do the right thing...
idp = (__u64 __user *)arg;id = ns->ns_id;return put_user(id, idp);- } }
/* extensible ioctls */ diff --git a/include/uapi/linux/nsfs.h b/include/uapi/linux/nsfs.h index 97d8d80d139f..f7c21840cc09 100644 --- a/include/uapi/linux/nsfs.h +++ b/include/uapi/linux/nsfs.h @@ -16,8 +16,6 @@ #define NS_GET_NSTYPE _IO(NSIO, 0x3) /* Get owner UID (in the caller's user namespace) for a user namespace */ #define NS_GET_OWNER_UID _IO(NSIO, 0x4) -/* Get the id for a mount namespace */ -#define NS_GET_MNTNS_ID _IOR(NSIO, 0x5, __u64) /* Translate pid from target pid namespace into the caller's pid namespace. */ #define NS_GET_PID_FROM_PIDNS _IOR(NSIO, 0x6, int) /* Return thread-group leader id of pid in the callers pid namespace. */ @@ -42,6 +40,16 @@ struct mnt_ns_info { /* Get previous namespace. */ #define NS_MNT_GET_PREV _IOR(NSIO, 12, struct mnt_ns_info) +/* Retrieve namespace identifiers. */ +#define NS_GET_MNTNS_ID _IOR(NSIO, 5, __u64) +#define NS_GET_NETNS_ID _IOR(NSIO, 13, __u64) +#define NS_GET_CGROUPNS_ID _IOR(NSIO, 14, __u64) +#define NS_GET_IPCNS_ID _IOR(NSIO, 15, __u64) +#define NS_GET_UTSNS_ID _IOR(NSIO, 16, __u64) +#define NS_GET_PIDNS_ID _IOR(NSIO, 17, __u64) +#define NS_GET_TIMENS_ID _IOR(NSIO, 18, __u64) +#define NS_GET_USERNS_ID _IOR(NSIO, 19, __u64)
enum init_ns_ino { IPC_NS_INIT_INO = 0xEFFFFFFFU, UTS_NS_INIT_INO = 0xEFFFFFFEU,
-- 2.47.3