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signalfuncs.c
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1 /*-------------------------------------------------------------------------
2  *
3  * signalfuncs.c
4  * Functions for signaling backends
5  *
6  * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
7  * Portions Copyright (c) 1994, Regents of the University of California
8  *
9  *
10  * IDENTIFICATION
11  * src/backend/storage/ipc/signalfuncs.c
12  *
13  *-------------------------------------------------------------------------
14  */
15 #include "postgres.h"
16 
17 #include <signal.h>
18 
19 #include "catalog/pg_authid.h"
20 #include "miscadmin.h"
21 #include "pgstat.h"
22 #include "postmaster/syslogger.h"
23 #include "storage/pmsignal.h"
24 #include "storage/proc.h"
25 #include "storage/procarray.h"
26 #include "utils/acl.h"
27 #include "utils/builtins.h"
28 
29 
30 /*
31  * Send a signal to another backend.
32  *
33  * The signal is delivered if the user is either a superuser or the same
34  * role as the backend being signaled. For "dangerous" signals, an explicit
35  * check for superuser needs to be done prior to calling this function.
36  *
37  * Returns 0 on success, 1 on general failure, 2 on normal permission error
38  * and 3 if the caller needs to be a superuser.
39  *
40  * In the event of a general failure (return code 1), a warning message will
41  * be emitted. For permission errors, doing that is the responsibility of
42  * the caller.
43  */
44 #define SIGNAL_BACKEND_SUCCESS 0
45 #define SIGNAL_BACKEND_ERROR 1
46 #define SIGNAL_BACKEND_NOPERMISSION 2
47 #define SIGNAL_BACKEND_NOSUPERUSER 3
48 static int
49 pg_signal_backend(int pid, int sig)
50 {
51  PGPROC *proc = BackendPidGetProc(pid);
52 
53  /*
54  * BackendPidGetProc returns NULL if the pid isn't valid; but by the time
55  * we reach kill(), a process for which we get a valid proc here might
56  * have terminated on its own. There's no way to acquire a lock on an
57  * arbitrary process to prevent that. But since so far all the callers of
58  * this mechanism involve some request for ending the process anyway, that
59  * it might end on its own first is not a problem.
60  */
61  if (proc == NULL)
62  {
63  /*
64  * This is just a warning so a loop-through-resultset will not abort
65  * if one backend terminated on its own during the run.
66  */
68  (errmsg("PID %d is not a PostgreSQL server process", pid)));
69  return SIGNAL_BACKEND_ERROR;
70  }
71 
72  /* Only allow superusers to signal superuser-owned backends. */
73  if (superuser_arg(proc->roleId) && !superuser())
75 
76  /* Users can signal backends they have role membership in. */
77  if (!has_privs_of_role(GetUserId(), proc->roleId) &&
78  !has_privs_of_role(GetUserId(), ROLE_PG_SIGNAL_BACKEND))
80 
81  /*
82  * Can the process we just validated above end, followed by the pid being
83  * recycled for a new process, before reaching here? Then we'd be trying
84  * to kill the wrong thing. Seems near impossible when sequential pid
85  * assignment and wraparound is used. Perhaps it could happen on a system
86  * where pid re-use is randomized. That race condition possibility seems
87  * too unlikely to worry about.
88  */
89 
90  /* If we have setsid(), signal the backend's whole process group */
91 #ifdef HAVE_SETSID
92  if (kill(-pid, sig))
93 #else
94  if (kill(pid, sig))
95 #endif
96  {
97  /* Again, just a warning to allow loops */
99  (errmsg("could not send signal to process %d: %m", pid)));
100  return SIGNAL_BACKEND_ERROR;
101  }
102  return SIGNAL_BACKEND_SUCCESS;
103 }
104 
105 /*
106  * Signal to cancel a backend process. This is allowed if you are a member of
107  * the role whose process is being canceled.
108  *
109  * Note that only superusers can signal superuser-owned processes.
110  */
111 Datum
113 {
114  int r = pg_signal_backend(PG_GETARG_INT32(0), SIGINT);
115 
117  ereport(ERROR,
118  (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
119  errmsg("must be a superuser to cancel superuser query")));
120 
122  ereport(ERROR,
123  (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
124  errmsg("must be a member of the role whose query is being canceled or member of pg_signal_backend")));
125 
127 }
128 
129 /*
130  * Wait until there is no backend process with the given PID and return true.
131  * On timeout, a warning is emitted and false is returned.
132  */
133 static bool
134 pg_wait_until_termination(int pid, int64 timeout)
135 {
136  /*
137  * Wait in steps of waittime milliseconds until this function exits or
138  * timeout.
139  */
140  int64 waittime = 100;
141 
142  /*
143  * Initially remaining time is the entire timeout specified by the user.
144  */
145  int64 remainingtime = timeout;
146 
147  /*
148  * Check existence of the backend. If the backend still exists, then wait
149  * for waittime milliseconds, again check for the existence. Repeat this
150  * until timeout or an error occurs or a pending interrupt such as query
151  * cancel gets processed.
152  */
153  do
154  {
155  if (remainingtime < waittime)
156  waittime = remainingtime;
157 
158  if (kill(pid, 0) == -1)
159  {
160  if (errno == ESRCH)
161  return true;
162  else
163  ereport(ERROR,
164  (errcode(ERRCODE_INTERNAL_ERROR),
165  errmsg("could not check the existence of the backend with PID %d: %m",
166  pid)));
167  }
168 
169  /* Process interrupts, if any, before waiting */
171 
172  (void) WaitLatch(MyLatch,
174  waittime,
176 
178 
179  remainingtime -= waittime;
180  } while (remainingtime > 0);
181 
183  (errmsg_plural("backend with PID %d did not terminate within %lld millisecond",
184  "backend with PID %d did not terminate within %lld milliseconds",
185  timeout,
186  pid, (long long int) timeout)));
187 
188  return false;
189 }
190 
191 /*
192  * Send a signal to terminate a backend process. This is allowed if you are a
193  * member of the role whose process is being terminated. If the timeout input
194  * argument is 0, then this function just signals the backend and returns
195  * true. If timeout is nonzero, then it waits until no process has the given
196  * PID; if the process ends within the timeout, true is returned, and if the
197  * timeout is exceeded, a warning is emitted and false is returned.
198  *
199  * Note that only superusers can signal superuser-owned processes.
200  */
201 Datum
203 {
204  int pid;
205  int r;
206  int timeout; /* milliseconds */
207 
208  pid = PG_GETARG_INT32(0);
209  timeout = PG_GETARG_INT64(1);
210 
211  if (timeout < 0)
212  ereport(ERROR,
213  (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
214  errmsg("\"timeout\" must not be negative")));
215 
216  r = pg_signal_backend(pid, SIGTERM);
217 
219  ereport(ERROR,
220  (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
221  errmsg("must be a superuser to terminate superuser process")));
222 
224  ereport(ERROR,
225  (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
226  errmsg("must be a member of the role whose process is being terminated or member of pg_signal_backend")));
227 
228  /* Wait only on success and if actually requested */
229  if (r == SIGNAL_BACKEND_SUCCESS && timeout > 0)
231  else
233 }
234 
235 /*
236  * Signal to reload the database configuration
237  *
238  * Permission checking for this function is managed through the normal
239  * GRANT system.
240  */
241 Datum
243 {
244  if (kill(PostmasterPid, SIGHUP))
245  {
247  (errmsg("failed to send signal to postmaster: %m")));
248  PG_RETURN_BOOL(false);
249  }
250 
251  PG_RETURN_BOOL(true);
252 }
253 
254 
255 /*
256  * Rotate log file
257  *
258  * This function is kept to support adminpack 1.0.
259  */
260 Datum
262 {
263  if (!superuser())
264  ereport(ERROR,
265  (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
266  errmsg("must be superuser to rotate log files with adminpack 1.0"),
267  /* translator: %s is a SQL function name */
268  errhint("Consider using %s, which is part of core, instead.",
269  "pg_logfile_rotate()")));
270 
271  if (!Logging_collector)
272  {
274  (errmsg("rotation not possible because log collection not active")));
275  PG_RETURN_BOOL(false);
276  }
277 
279  PG_RETURN_BOOL(true);
280 }
281 
282 /*
283  * Rotate log file
284  *
285  * Permission checking for this function is managed through the normal
286  * GRANT system.
287  */
288 Datum
290 {
291  if (!Logging_collector)
292  {
294  (errmsg("rotation not possible because log collection not active")));
295  PG_RETURN_BOOL(false);
296  }
297 
299  PG_RETURN_BOOL(true);
300 }
Datum pg_rotate_logfile(PG_FUNCTION_ARGS)
Definition: signalfuncs.c:261
#define PG_GETARG_INT32(n)
Definition: fmgr.h:269
int errhint(const char *fmt,...)
Definition: elog.c:1156
Datum pg_rotate_logfile_v2(PG_FUNCTION_ARGS)
Definition: signalfuncs.c:289
#define WL_TIMEOUT
Definition: latch.h:128
Oid GetUserId(void)
Definition: miscinit.c:495
int errmsg_plural(const char *fmt_singular, const char *fmt_plural, unsigned long n,...)
Definition: elog.c:1019
PGPROC * BackendPidGetProc(int pid)
Definition: procarray.c:3133
bool has_privs_of_role(Oid member, Oid role)
Definition: acl.c:4843
Oid roleId
Definition: proc.h:155
int errcode(int sqlerrcode)
Definition: elog.c:698
bool superuser(void)
Definition: superuser.c:46
#define kill(pid, sig)
Definition: win32_port.h:454
Datum pg_cancel_backend(PG_FUNCTION_ARGS)
Definition: signalfuncs.c:112
#define SIGNAL_BACKEND_SUCCESS
Definition: signalfuncs.c:44
void ResetLatch(Latch *latch)
Definition: latch.c:660
int WaitLatch(Latch *latch, int wakeEvents, long timeout, uint32 wait_event_info)
Definition: latch.c:452
static int pg_signal_backend(int pid, int sig)
Definition: signalfuncs.c:49
bool Logging_collector
Definition: syslogger.c:71
#define SIGNAL_BACKEND_NOSUPERUSER
Definition: signalfuncs.c:47
#define ERROR
Definition: elog.h:46
#define SIGHUP
Definition: win32_port.h:159
bool superuser_arg(Oid roleid)
Definition: superuser.c:56
#define SIGNAL_BACKEND_NOPERMISSION
Definition: signalfuncs.c:46
Datum pg_reload_conf(PG_FUNCTION_ARGS)
Definition: signalfuncs.c:242
pid_t PostmasterPid
Definition: globals.c:98
#define WARNING
Definition: elog.h:40
static bool pg_wait_until_termination(int pid, int64 timeout)
Definition: signalfuncs.c:134
#define PG_RETURN_BOOL(x)
Definition: fmgr.h:359
uintptr_t Datum
Definition: postgres.h:411
#define SIGNAL_BACKEND_ERROR
Definition: signalfuncs.c:45
static int sig
Definition: pg_ctl.c:84
#define ereport(elevel,...)
Definition: elog.h:157
int errmsg(const char *fmt,...)
Definition: elog.c:909
Datum pg_terminate_backend(PG_FUNCTION_ARGS)
Definition: signalfuncs.c:202
struct Latch * MyLatch
Definition: globals.c:57
#define PG_FUNCTION_ARGS
Definition: fmgr.h:193
#define CHECK_FOR_INTERRUPTS()
Definition: miscadmin.h:120
void SendPostmasterSignal(PMSignalReason reason)
Definition: pmsignal.c:153
#define PG_GETARG_INT64(n)
Definition: fmgr.h:283
Definition: proc.h:121
#define WL_LATCH_SET
Definition: latch.h:125
#define WL_EXIT_ON_PM_DEATH
Definition: latch.h:130