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Introduce pg_signal_autovacuum_worker.

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Since commit 3a9b18b309, roles with privileges of pg_signal_backend
cannot signal autovacuum workers.  Many users treated the ability
to signal autovacuum workers as a feature instead of a bug, so we
are reintroducing it via a new predefined role.  Having privileges
of this new role, named pg_signal_autovacuum_worker, only permits
signaling autovacuum workers.  It does not permit signaling other
types of superuser backends.

Bumps catversion.

Author: Kirill Reshke
Reviewed-by: Anthony Leung, Michael Paquier, Andrey Borodin
Discussion: https://postgr.es/m/CALdSSPhC4GGmbnugHfB9G0%3DfAxjCSug_-rmL9oUh0LTxsyBfsg%40mail.gmail.com
This commit is contained in:
Nathan Bossart
2024-07-09 13:03:40 -05:00
parent 629520be5f
commit ccd38024bc
5 changed files with 56 additions and 10 deletions
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46
src/backend/storage/ipc/signalfuncs.c
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@@ -34,8 +34,9 @@
* role as the backend being signaled. For "dangerous" signals, an explicit
* check for superuser needs to be done prior to calling this function.
*
* Returns 0 on success, 1 on general failure, 2 on normal permission error
* and 3 if the caller needs to be a superuser.
* Returns 0 on success, 1 on general failure, 2 on normal permission error,
* 3 if the caller needs to be a superuser, and 4 if the caller needs to have
* privileges of pg_signal_autovacuum_worker.
*
* In the event of a general failure (return code 1), a warning message will
* be emitted. For permission errors, doing that is the responsibility of
@@ -45,6 +46,7 @@
#define SIGNAL_BACKEND_ERROR 1
#define SIGNAL_BACKEND_NOPERMISSION 2
#define SIGNAL_BACKEND_NOSUPERUSER 3
#define SIGNAL_BACKEND_NOAUTOVAC 4
static int
pg_signal_backend(int pid, int sig)
{
@@ -77,15 +79,27 @@ pg_signal_backend(int pid, int sig)
/*
* Only allow superusers to signal superuser-owned backends. Any process
* not advertising a role might have the importance of a superuser-owned
* backend, so treat it that way.
* backend, so treat it that way. As an exception, we allow roles with
* privileges of pg_signal_autovacuum_worker to signal autovacuum workers
* (which do not advertise a role).
*
* Otherwise, users can signal backends for roles they have privileges of.
*/
if ((!OidIsValid(proc->roleId) || superuser_arg(proc->roleId)) &&
!superuser())
return SIGNAL_BACKEND_NOSUPERUSER;
if (!OidIsValid(proc->roleId) || superuser_arg(proc->roleId))
{
ProcNumber procNumber = GetNumberFromPGProc(proc);
PgBackendStatus *procStatus = pgstat_get_beentry_by_proc_number(procNumber);
/* Users can signal backends they have role membership in. */
if (!has_privs_of_role(GetUserId(), proc->roleId) &&
!has_privs_of_role(GetUserId(), ROLE_PG_SIGNAL_BACKEND))
if (procStatus && procStatus->st_backendType == B_AUTOVAC_WORKER)
{
if (!has_privs_of_role(GetUserId(), ROLE_PG_SIGNAL_AUTOVACUUM_WORKER))
return SIGNAL_BACKEND_NOAUTOVAC;
}
else if (!superuser())
return SIGNAL_BACKEND_NOSUPERUSER;
}
else if (!has_privs_of_role(GetUserId(), proc->roleId) &&
!has_privs_of_role(GetUserId(), ROLE_PG_SIGNAL_BACKEND))
return SIGNAL_BACKEND_NOPERMISSION;
/*
@@ -130,6 +144,13 @@ pg_cancel_backend(PG_FUNCTION_ARGS)
errdetail("Only roles with the %s attribute may cancel queries of roles with the %s attribute.",
"SUPERUSER", "SUPERUSER")));
if (r == SIGNAL_BACKEND_NOAUTOVAC)
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("permission denied to cancel query"),
errdetail("Only roles with privileges of the \"%s\" role may cancel autovacuum workers.",
"pg_signal_autovacuum_worker")));
if (r == SIGNAL_BACKEND_NOPERMISSION)
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
@@ -236,6 +257,13 @@ pg_terminate_backend(PG_FUNCTION_ARGS)
errdetail("Only roles with the %s attribute may terminate processes of roles with the %s attribute.",
"SUPERUSER", "SUPERUSER")));
if (r == SIGNAL_BACKEND_NOAUTOVAC)
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("permission denied to terminate process"),
errdetail("Only roles with privileges of the \"%s\" role may terminate autovacuum workers.",
"pg_signal_autovacuum_worker")));
if (r == SIGNAL_BACKEND_NOPERMISSION)
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),