liveupdate: add LIVEUPDATE_SESSION_GET_NAME ioctl

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>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Link: https://lore.kernel.org/r/20260429212221.814107-4-luca.boccassi@gmail.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

diff --git a/include/uapi/linux/liveupdate.h b/include/uapi/linux/liveupdate.h
index 30bc66ee9436a0a052ce038a6418c2998bcd6ace..3a9ff53b02e00b5604b890c6458c1b6fe583e075 100644 (file)
--- 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 ec7aebc15a8016ad2ac7af80a0b12e7e6aae14fe..e7f27815c051722b35e76d6312d5589a57574f76 100644 (file)
--- a/kernel/liveupdate/luo_session.c
+++ b/kernel/liveupdate/luo_session.c
@@ -289,10 +289,24 @@ 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;
+
+       if (argp->reserved != 0)
+               return -EINVAL;
+
+       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 +333,8 @@ 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,