Thread: innocuous: pgbench does FD_ISSET on invalid socket
I noticed that pgbench calls FD_ISSET on a socket returned by
PQsocket() without first checking that it's not invalid. I don't think
there's a real problem here because the socket was already checked a few
lines above, but I think applying the same coding pattern to both places
is cleaner.
Any objections to changing it like this? I'd probably backpatch to 9.5,
but no further (even though this pattern actually appears all the way
back.)
*** a/src/bin/pgbench/pgbench.c
--- b/src/bin/pgbench/pgbench.c
***************
*** 3770,3780 **** threadRun(void *arg) Command **commands = sql_script[st->use_file].commands;
int prev_ecnt = st->ecnt;
! if (st->con && (FD_ISSET(PQsocket(st->con), &input_mask)
! || commands[st->state]->type == META_COMMAND)) {
! if (!doCustom(thread, st, &aggs))
! remains--; /* I've aborted */ } if (st->ecnt > prev_ecnt &&
commands[st->state]->type== META_COMMAND)
--- 3770,3790 ---- Command **commands = sql_script[st->use_file].commands; int
prev_ecnt= st->ecnt;
! if (st->con) {
! int sock = PQsocket(st->con);
!
! if (sock < 0)
! {
! fprintf(stderr, "bad socket: %s\n", strerror(errno));
! goto done;
! }
! if (FD_ISSET(sock, &input_mask) ||
! commands[st->state]->type == META_COMMAND)
! {
! if (!doCustom(thread, st, &aggs))
! remains--; /* I've aborted */
! } } if (st->ecnt > prev_ecnt && commands[st->state]->type == META_COMMAND)
--
Álvaro Herrera http://www.linkedin.com/in/alvherre
On Sat, Feb 13, 2016 at 6:25 AM, Alvaro Herrera <alvherre@alvh.no-ip.org> wrote: > I noticed that pgbench calls FD_ISSET on a socket returned by > PQsocket() without first checking that it's not invalid. I don't think > there's a real problem here because the socket was already checked a few > lines above, but I think applying the same coding pattern to both places > is cleaner. > > Any objections to changing it like this? I'd probably backpatch to 9.5, > but no further (even though this pattern actually appears all the way > back.) Not really, +1 for consistency here, and this makes the code clearer. Different issues in the same area: 1) In vacuumdb.c, init_slot() does not check for the return value of PQsocket(): slot->sock = PQsocket(conn); 2) In isolationtester.c, try_complete_step() should do the same. 3) In pg_recvlogical.c for StreamLogicalLog() I am spotting the same problem. I guess those ones should be fixed as well, no? -- Michael
On Mon, Feb 15, 2016 at 3:20 PM, Michael Paquier <michael.paquier@gmail.com> wrote: > On Sat, Feb 13, 2016 at 6:25 AM, Alvaro Herrera <alvherre@alvh.no-ip.org> wrote: >> I noticed that pgbench calls FD_ISSET on a socket returned by >> PQsocket() without first checking that it's not invalid. I don't think >> there's a real problem here because the socket was already checked a few >> lines above, but I think applying the same coding pattern to both places >> is cleaner. >> >> Any objections to changing it like this? I'd probably backpatch to 9.5, >> but no further (even though this pattern actually appears all the way >> back.) > > Not really, +1 for consistency here, and this makes the code clearer. > > Different issues in the same area: > 1) In vacuumdb.c, init_slot() does not check for the return value of PQsocket(): > slot->sock = PQsocket(conn); > 2) In isolationtester.c, try_complete_step() should do the same. > 3) In pg_recvlogical.c for StreamLogicalLog() I am spotting the same problem. > I guess those ones should be fixed as well, no? With a patch, that's even better. -- Michael
Attachment
Hello Alvaro, > Any objections to changing it like this? I'd probably backpatch to 9.5, > but no further (even though this pattern actually appears all the way > back.) My 0.02€: if the pattern is repeated, maybe a function which incorporates the check would save lines and improve overall readability? ... = safePQsocket(...); -- Fabien.
I noticed that strerror(errno) wasn't the most helpful error context ever, so I changed it to PQerrorMessage(). There may be room for additional improvement there. I also noticed that if one connection dies, we terminate the whole thread, and if the thread is serving multiple connections, the other ones are not PQfinished. It may or may not be worthwhile improving this; if pgbench is used to test the server when connections are randomly dropped that would be helpful, otherwise not so much. I ended up backpatching all the way back. Fabien COELHO wrote: > > Hello Alvaro, > > >Any objections to changing it like this? I'd probably backpatch to 9.5, > >but no further (even though this pattern actually appears all the way > >back.) > > My 0.02€: if the pattern is repeated, maybe a function which incorporates > the check would save lines and improve overall readability? > > ... = safePQsocket(...); Hmm, yeah, but that doesn't work too well because we're not invoking exit() in case of an error (which is what the safe pg_malloc etc do), so we'd have to check for what to do after safePQsocket returns -- no improvement in code clarity IMHO. Thanks for the suggestion. Michael Paquier wrote: > Different issues in the same area: > 1) In vacuumdb.c, init_slot() does not check for the return value of PQsocket(): > slot->sock = PQsocket(conn); > 2) In isolationtester.c, try_complete_step() should do the same. > 3) In pg_recvlogical.c for StreamLogicalLog() I am spotting the same problem. > I guess those ones should be fixed as well, no? Hmm, yeah, perhaps it's worth closing these too. -- Álvaro Herrera http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
On Tue, Feb 16, 2016 at 8:47 AM, Alvaro Herrera <alvherre@2ndquadrant.com> wrote: > Michael Paquier wrote: > >> Different issues in the same area: >> 1) In vacuumdb.c, init_slot() does not check for the return value of PQsocket(): >> slot->sock = PQsocket(conn); >> 2) In isolationtester.c, try_complete_step() should do the same. >> 3) In pg_recvlogical.c for StreamLogicalLog() I am spotting the same problem. >> I guess those ones should be fixed as well, no? > > Hmm, yeah, perhaps it's worth closing these too. Do you think that it would be better starting a new thread? The only difficulty of this patch is to be sure that each error handling is done correctly for each one of those frontend modules. -- Michael