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Commitc4a586c

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Prevent possible crash reading pg_stat_activity.
Also, avoid reading PGPROC's wait_event field twice, once for the waitevent and again for the wait_event_type, because the value might changein the middle.Petr Jelinek and Robert Haas
1 parent36f69fa commitc4a586c

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1 file changed

+21
-12
lines changed

1 file changed

+21
-12
lines changed

‎src/backend/utils/adt/pgstatfuncs.c

Lines changed: 21 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -27,6 +27,8 @@
2727
#include"utils/inet.h"
2828
#include"utils/timestamp.h"
2929

30+
#defineUINT32_ACCESS_ONCE(var) ((uint32)(*((volatile uint32 *)&(var))))
31+
3032
/* bogus ... these externs should be in a header file */
3133
externDatumpg_stat_get_numscans(PG_FUNCTION_ARGS);
3234
externDatumpg_stat_get_tuples_returned(PG_FUNCTION_ARGS);
@@ -783,13 +785,26 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
783785
values[5]=CStringGetTextDatum(beentry->st_activity);
784786

785787
proc=BackendPidGetProc(beentry->st_procpid);
786-
wait_event_type=pgstat_get_wait_event_type(proc->wait_event_info);
788+
if (proc!=NULL)
789+
{
790+
uint32raw_wait_event;
791+
792+
raw_wait_event=UINT32_ACCESS_ONCE(proc->wait_event_info);
793+
wait_event_type=pgstat_get_wait_event_type(raw_wait_event);
794+
wait_event=pgstat_get_wait_event(raw_wait_event);
795+
796+
}
797+
else
798+
{
799+
wait_event_type=NULL;
800+
wait_event=NULL;
801+
}
802+
787803
if (wait_event_type)
788804
values[6]=CStringGetTextDatum(wait_event_type);
789805
else
790806
nulls[6]= true;
791807

792-
wait_event=pgstat_get_wait_event(proc->wait_event_info);
793808
if (wait_event)
794809
values[7]=CStringGetTextDatum(wait_event);
795810
else
@@ -984,17 +999,14 @@ pg_stat_get_backend_wait_event_type(PG_FUNCTION_ARGS)
984999
int32beid=PG_GETARG_INT32(0);
9851000
PgBackendStatus*beentry;
9861001
PGPROC*proc;
987-
constchar*wait_event_type;
1002+
constchar*wait_event_type=NULL;
9881003

9891004
if ((beentry=pgstat_fetch_stat_beentry(beid))==NULL)
9901005
wait_event_type="<backend information not available>";
9911006
elseif (!has_privs_of_role(GetUserId(),beentry->st_userid))
9921007
wait_event_type="<insufficient privilege>";
993-
else
994-
{
995-
proc=BackendPidGetProc(beentry->st_procpid);
1008+
elseif ((proc=BackendPidGetProc(beentry->st_procpid))!=NULL)
9961009
wait_event_type=pgstat_get_wait_event_type(proc->wait_event_info);
997-
}
9981010

9991011
if (!wait_event_type)
10001012
PG_RETURN_NULL();
@@ -1008,17 +1020,14 @@ pg_stat_get_backend_wait_event(PG_FUNCTION_ARGS)
10081020
int32beid=PG_GETARG_INT32(0);
10091021
PgBackendStatus*beentry;
10101022
PGPROC*proc;
1011-
constchar*wait_event;
1023+
constchar*wait_event=NULL;
10121024

10131025
if ((beentry=pgstat_fetch_stat_beentry(beid))==NULL)
10141026
wait_event="<backend information not available>";
10151027
elseif (!has_privs_of_role(GetUserId(),beentry->st_userid))
10161028
wait_event="<insufficient privilege>";
1017-
else
1018-
{
1019-
proc=BackendPidGetProc(beentry->st_procpid);
1029+
elseif ((proc=BackendPidGetProc(beentry->st_procpid))!=NULL)
10201030
wait_event=pgstat_get_wait_event(proc->wait_event_info);
1021-
}
10221031

10231032
if (!wait_event)
10241033
PG_RETURN_NULL();

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