[PATCH v10 3/4] liveupdate: add LIVEUPDATE_SESSION_GET_NAME ioctl

luca.boccassi
2026-04-23T23:49:06Z

From: Luca Boccassi <luca.boccassi@gmail.com>

Userspace when requesting a session via the ioctl specifies a name and
gets a FD, but then there is no ioctl to go back the other way and get
the name given a LUO session FD. This is problematic especially when
there is a userspace orchestrator that wants to check what FDs it is
handling for clients without having to do manual string scraping of
procfs, or without procfs at all.

Add a ioctl to simply get the name from an FD.

Signed-off-by: Luca Boccassi <luca.boccassi@gmail.com>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
include/uapi/linux/liveupdate.h | 21 +++++++++++++++++++++
kernel/liveupdate/luo_session.c | 13 +++++++++++++
2 files changed, 34 insertions(+)

diff --git a/include/uapi/linux/liveupdate.h b/include/uapi/linux/liveupdate.h
index 30bc66ee9436..3a9ff53b02e0 100644
--- a/include/uapi/linux/liveupdate.h
+++ b/include/uapi/linux/liveupdate.h
@@ -59,6 +59,7 @@ enum {
LIVEUPDATE_CMD_SESSION_PRESERVE_FD = LIVEUPDATE_CMD_SESSION_BASE,
LIVEUPDATE_CMD_SESSION_RETRIEVE_FD = 0x41,
LIVEUPDATE_CMD_SESSION_FINISH = 0x42,
+ LIVEUPDATE_CMD_SESSION_GET_NAME = 0x43,
};

/**
@@ -213,4 +214,24 @@ struct liveupdate_session_finish {
#define LIVEUPDATE_SESSION_FINISH \
_IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_SESSION_FINISH)

+/**
+ * struct liveupdate_session_get_name - ioctl(LIVEUPDATE_SESSION_GET_NAME)
+ * @size: Input; sizeof(struct liveupdate_session_get_name)
+ * @reserved: Input; Must be zero. Reserved for future use.
+ * @name: Output; A null-terminated string with the full session name.
+ *
+ * Retrieves the full name of the session associated with this file descriptor.
+ * This is useful because the kernel may truncate the name shown in /proc.
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+struct liveupdate_session_get_name {
+ __u32 size;
+ __u32 reserved;
+ __u8 name[LIVEUPDATE_SESSION_NAME_LENGTH];
+};
+
+#define LIVEUPDATE_SESSION_GET_NAME \
+ _IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_SESSION_GET_NAME)
+
#endif /* _UAPI_LIVEUPDATE_H */
diff --git a/kernel/liveupdate/luo_session.c b/kernel/liveupdate/luo_session.c
index 5e316a4c5d71..0bcf2def074e 100644
--- a/kernel/liveupdate/luo_session.c
+++ b/kernel/liveupdate/luo_session.c
@@ -289,10 +289,21 @@ static int luo_session_finish(struct luo_session *session,
return luo_ucmd_respond(ucmd, sizeof(*argp));
}

+static int luo_session_get_name(struct luo_session *session,
+ struct luo_ucmd *ucmd)
+{
+ struct liveupdate_session_get_name *argp = ucmd->cmd;
+
+ strscpy((char *)argp->name, session->name, sizeof(argp->name));
+
+ return luo_ucmd_respond(ucmd, sizeof(*argp));
+}
+
union ucmd_buffer {
struct liveupdate_session_finish finish;
struct liveupdate_session_preserve_fd preserve;
struct liveupdate_session_retrieve_fd retrieve;
+ struct liveupdate_session_get_name get_name;
};

struct luo_ioctl_op {
@@ -319,6 +330,8 @@ static const struct luo_ioctl_op luo_session_ioctl_ops[] = {
struct liveupdate_session_preserve_fd, token),
IOCTL_OP(LIVEUPDATE_SESSION_RETRIEVE_FD, luo_session_retrieve_fd,
struct liveupdate_session_retrieve_fd, token),
+ IOCTL_OP(LIVEUPDATE_SESSION_GET_NAME, luo_session_get_name,
+ struct liveupdate_session_get_name, name),
};

static long luo_session_ioctl(struct file *filep, unsigned int cmd,
--
2.47.3