Commit 02b51df1b07b4e9ca823c89284e704cadb323cd1

Authored by Scott James Remnant
Committed by Linus Torvalds
1 parent 88e9d34c72

proc connector: add event for process becoming session leader

The act of a process becoming a session leader is a useful signal to a
supervising init daemon such as Upstart.

While a daemon will normally do this as part of the process of becoming a
daemon, it is rare for its children to do so.  When the children do, it is
nearly always a sign that the child should be considered detached from the
parent and not supervised along with it.

The poster-child example is OpenSSH; the per-login children call setsid()
so that they may control the pty connected to them.  If the primary daemon
dies or is restarted, we do not want to consider the per-login children
and want to respawn the primary daemon without killing the children.

This patch adds a new PROC_SID_EVENT and associated structure to the
proc_event event_data union, it arranges for this to be emitted when the
special PIDTYPE_SID pid is set.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Scott James Remnant <scott@ubuntu.com>
Acked-by: Matt Helsley <matthltc@us.ibm.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Acked-by: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Showing 3 changed files with 38 additions and 1 deletions Side-by-side Diff

drivers/connector/cn_proc.c
... ... @@ -139,6 +139,31 @@
139 139 cn_netlink_send(msg, CN_IDX_PROC, GFP_KERNEL);
140 140 }
141 141  
  142 +void proc_sid_connector(struct task_struct *task)
  143 +{
  144 + struct cn_msg *msg;
  145 + struct proc_event *ev;
  146 + struct timespec ts;
  147 + __u8 buffer[CN_PROC_MSG_SIZE];
  148 +
  149 + if (atomic_read(&proc_event_num_listeners) < 1)
  150 + return;
  151 +
  152 + msg = (struct cn_msg *)buffer;
  153 + ev = (struct proc_event *)msg->data;
  154 + get_seq(&msg->seq, &ev->cpu);
  155 + ktime_get_ts(&ts); /* get high res monotonic timestamp */
  156 + put_unaligned(timespec_to_ns(&ts), (__u64 *)&ev->timestamp_ns);
  157 + ev->what = PROC_EVENT_SID;
  158 + ev->event_data.sid.process_pid = task->pid;
  159 + ev->event_data.sid.process_tgid = task->tgid;
  160 +
  161 + memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));
  162 + msg->ack = 0; /* not used */
  163 + msg->len = sizeof(*ev);
  164 + cn_netlink_send(msg, CN_IDX_PROC, GFP_KERNEL);
  165 +}
  166 +
142 167 void proc_exit_connector(struct task_struct *task)
143 168 {
144 169 struct cn_msg *msg;
include/linux/cn_proc.h
... ... @@ -52,6 +52,7 @@
52 52 PROC_EVENT_EXEC = 0x00000002,
53 53 PROC_EVENT_UID = 0x00000004,
54 54 PROC_EVENT_GID = 0x00000040,
  55 + PROC_EVENT_SID = 0x00000080,
55 56 /* "next" should be 0x00000400 */
56 57 /* "last" is the last process event: exit */
57 58 PROC_EVENT_EXIT = 0x80000000
... ... @@ -89,6 +90,11 @@
89 90 } e;
90 91 } id;
91 92  
  93 + struct sid_proc_event {
  94 + __kernel_pid_t process_pid;
  95 + __kernel_pid_t process_tgid;
  96 + } sid;
  97 +
92 98 struct exit_proc_event {
93 99 __kernel_pid_t process_pid;
94 100 __kernel_pid_t process_tgid;
... ... @@ -102,6 +108,7 @@
102 108 void proc_fork_connector(struct task_struct *task);
103 109 void proc_exec_connector(struct task_struct *task);
104 110 void proc_id_connector(struct task_struct *task, int which_id);
  111 +void proc_sid_connector(struct task_struct *task);
105 112 void proc_exit_connector(struct task_struct *task);
106 113 #else
107 114 static inline void proc_fork_connector(struct task_struct *task)
... ... @@ -112,6 +119,9 @@
112 119  
113 120 static inline void proc_id_connector(struct task_struct *task,
114 121 int which_id)
  122 +{}
  123 +
  124 +static inline void proc_sid_connector(struct task_struct *task)
115 125 {}
116 126  
117 127 static inline void proc_exit_connector(struct task_struct *task)
... ... @@ -359,8 +359,10 @@
359 359 {
360 360 struct task_struct *curr = current->group_leader;
361 361  
362   - if (task_session(curr) != pid)
  362 + if (task_session(curr) != pid) {
363 363 change_pid(curr, PIDTYPE_SID, pid);
  364 + proc_sid_connector(curr);
  365 + }
364 366  
365 367 if (task_pgrp(curr) != pid)
366 368 change_pid(curr, PIDTYPE_PGID, pid);