Ticket History #7454: select on set of all bad fds

On 12-11-28 17:46, Greg Hudson via RT <rt-comment@krbdev.mit.edu> wrote:

Yes, but you are right, its poll(), here is what strace -p on such a process says:
poll([{fd=4, events=POLLIN}, {fd=10, events=POLLIN}], 2, 1779582387) = 2 ([{fd=4, revents=POLLIN}, {fd=10, revents=POLLIN}])
(repeated ad infinitum)


For the full gdb session, see below.

In sendto_kdc.c line 1169, after cm_select_or_poll, there is a number of
fds in selstate, as you can see below. But the 'state->fd' of the only
connection in 'conns' is INVALID_SOCKET (see line 1179), so the for-loop
always calls continue and never calls state->service() to handle data on
the fds. Our patch detects if all connections in 'conns' are in the
INVALID_SOCKET state and exits.


Ciao,

Alexander Wuerstlein.


----

(gdb) bt
#0 0x00007f4a58e1ea88 in *__GI___poll (fds=fds@entry=0x7f4a5ad38ab8, nfds=2, timeout=<optimized out>, timeout@entry=1778794454)
at ../sysdeps/unix/sysv/linux/poll.c:83
#1 0x00007f4a59358004 in cm_select_or_poll (sret=<synthetic pointer>, out=0x7f4a5ad38ab8, in=0x7f4a5ad36aa0) at ../../../../src/lib/krb5/os/sendto_kdc.c:530
#2 service_fds (context=context@entry=0x7f4a5ad252e0, selstate=selstate@entry=0x7f4a5ad36aa0, interval=interval@entry=1, conns=conns@entry=0x7f4a5ad3be80,
seltemp=seltemp@entry=0x7f4a5ad38ab8, msg_handler=msg_handler@entry=0x7f4a59357880 <check_for_svc_unavailable>,
msg_handler_data=msg_handler_data@entry=0x7fff80e65c48, winner_out=winner_out@entry=0x7fff80e65b18) at ../../../../src/lib/krb5/os/sendto_kdc.c:1163
#3 0x00007f4a59358e5c in k5_sendto (context=context@entry=0x7f4a5ad252e0, message=message@entry=0x7fff80e65cd0, servers=servers@entry=0x7fff80e65c50,
socktype1=socktype1@entry=2, socktype2=1, callback_info=callback_info@entry=0x0, reply=reply@entry=0x7fff80e65ce0, remoteaddr=remoteaddr@entry=0x0,
remoteaddrlen=remoteaddrlen@entry=0x0, server_used=server_used@entry=0x7fff80e65c4c,
msg_handler=msg_handler@entry=0x7f4a59357880 <check_for_svc_unavailable>, msg_handler_data=msg_handler_data@entry=0x7fff80e65c48)
at ../../../../src/lib/krb5/os/sendto_kdc.c:1290
#4 0x00007f4a593592dc in krb5_sendto_kdc (context=context@entry=0x7f4a5ad252e0, message=message@entry=0x7fff80e65cd0, realm=realm@entry=0x7fff80e65cf0,
reply=reply@entry=0x7fff80e65ce0, use_master=use_master@entry=0x7fff80e65e08, tcp_only=tcp_only@entry=0) at ../../../../src/lib/krb5/os/sendto_kdc.c:339
#5 0x00007f4a59331efb in init_creds_get (context=context@entry=0x7f4a5ad252e0, ctx=0x7f4a5ad25b90, use_master=use_master@entry=0x7fff80e65e08)
at ../../../../src/lib/krb5/krb/get_in_tkt.c:578
#6 0x00007f4a5933202d in krb5int_get_init_creds (context=context@entry=0x7f4a5ad252e0, creds=creds@entry=0x7f4a5ad25a30, client=client@entry=0x7f4a5ad25980,
prompter=prompter@entry=0x7f4a576ae9e0, prompter_data=prompter_data@entry=0x7f4a5ad21ed0, start_time=start_time@entry=0,
in_tkt_service=in_tkt_service@entry=0x0, options=options@entry=0x7f4a5ad25ab0, gak_fct=gak_fct@entry=0x7f4a59332f80 <krb5_get_as_key_password>,
gak_data=gak_data@entry=0x7fff80e65e30, use_master=use_master@entry=0x7fff80e65e08, as_reply=as_reply@entry=0x7fff80e65e18)
at ../../../../src/lib/krb5/krb/get_in_tkt.c:1649
#7 0x00007f4a59333632 in krb5_get_init_creds_password (context=0x7f4a5ad252e0, creds=0x7f4a5ad25a30, client=0x7f4a5ad25980, password=<optimized out>,
prompter=0x7f4a576ae9e0, data=0x7f4a5ad21ed0, start_time=0, in_tkt_service=0x0, options=0x7f4a5ad25ab0) at ../../../../src/lib/krb5/krb/gic_pwd.c:291
#8 0x00007f4a576ac3e3 in ?? () from /lib/x86_64-linux-gnu/security/pam_krb5.so
#9 0x00007f4a576acb21 in ?? () from /lib/x86_64-linux-gnu/security/pam_krb5.so
#10 0x00007f4a576aef86 in pam_sm_authenticate () from /lib/x86_64-linux-gnu/security/pam_krb5.so
#11 0x00007f4a5a4471f5 in ?? () from /lib/x86_64-linux-gnu/libpam.so.0
#12 0x00007f4a5a446a78 in pam_authenticate () from /lib/x86_64-linux-gnu/libpam.so.0
#13 0x00007f4a5aaafb0d in ?? ()
#14 0x00007f4a5aaafda1 in ?? ()
#15 0x00007f4a5aaa3a55 in ?? ()
#16 0x00007f4a5aaa67ba in ?? ()
#17 0x00007f4a5aaa75dd in ?? ()
#18 0x00007f4a5aa8f103 in main ()
(gdb) p selstate
No symbol "selstate" in current context.
(gdb) list
78 in ../sysdeps/unix/sysv/linux/poll.c
(gdb) finish
Run till exit from #0 0x00007f4a58e1ea88 in *__GI___poll (fds=fds@entry=0x7f4a5ad38ab8, nfds=2, timeout=<optimized out>, timeout@entry=1778794454)
at ../sysdeps/unix/sysv/linux/poll.c:83
0x00007f4a59358004 in cm_select_or_poll (sret=<synthetic pointer>, out=0x7f4a5ad38ab8, in=0x7f4a5ad36aa0) at ../../../../src/lib/krb5/os/sendto_kdc.c:530
530 ../../../../src/lib/krb5/os/sendto_kdc.c: No such file or directory.
Value returned is $1 = 2
(gdb) finish
Run till exit from #0 0x00007f4a59358004 in cm_select_or_poll (sret=<synthetic pointer>, out=0x7f4a5ad38ab8, in=0x7f4a5ad36aa0)
at ../../../../src/lib/krb5/os/sendto_kdc.c:530
1169 in ../../../../src/lib/krb5/os/sendto_kdc.c
(gdb) p selstate
$2 = (struct select_state *) 0x7f4a5ad36aa0
(gdb) p *selstate
$3 = {fds = {{fd = 4, events = 1, revents = 26222}, {fd = 10, events = 1, revents = 29295}, {fd = 11, events = 5, revents = 30068}, {fd = 1702194477,
events = 25454, revents = 25960}, {fd = -1066876818, events = 71, revents = 1}, {fd = 1359020033, events = 128, revents = -31996}, {fd = -1066918212,
events = 71, revents = 28}, {fd = 1359020033, events = 128, revents = 8208}, {fd = 171443713, events = 0, revents = 542}, {fd = -16796891,
events = 21022, revents = -16142}, {fd = 65679, events = 1, revents = 20737}, {fd = -2096889728, events = 956, revents = -16382}, {fd = 65656,
events = 1, revents = 20737}, {fd = -2096889728, events = 3260, revents = -16284}, {fd = 65697, events = 1, revents = 513}, {fd = -2096889814,
events = 159, revents = 1}, {fd = 0, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 0,
events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 1634497125, events = 26478, revents = 28261}, {fd = 528, events = 0, revents = 0}, {
fd = 80, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 4, events = -7348, revents = 0}, {fd = -2132387920, events = 32767,
revents = 0}, {fd = 1496736238, events = 32586, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 1, events = 1, revents = 0}, {fd = 0,
events = 0, revents = 0}, {fd = 1, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 74849, events = 0, revents = 0}, {
fd = 1523804080, events = 32586, revents = 0}, {fd = 1143887169, events = 32581, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 0, events = 0,
revents = 0}, {fd = 48, events = 0, revents = 0}, {fd = 74801, events = 0, revents = 0}, {fd = 0, events = 32586, revents = 0}, {fd = 0, events = 0,
revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 0, events = 0,
revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 0, events = 0,
revents = 0}, {fd = 1494028800, events = 32586, revents = 0}, {fd = 74705, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {
fd = 1494034560, events = 32586, revents = 0}, {fd = -1, events = 2, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 0, events = 0,
revents = 0}, {fd = 1523805376, events = 32586, revents = 0}, {fd = -1, events = -1, revents = -1}, {fd = 0, events = 0, revents = 0}, {
fd = 1523805392, events = 32586, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0},
{fd = -1, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 1523804976, events = 32586, revents = 0}, {fd = 1494029568, events = 32586,
revents = 0}, {fd = 0, events = -1, revents = -1}, {fd = 0, events = 0, revents = 0} <repeats 18 times>, {fd = 16193, events = 0, revents = 0}, {
fd = 1494042040, events = 32586, revents = 0}, {fd = 1494042040, events = 32586, revents = 0}, {fd = 1523805520, events = 32586, revents = 0}, {
fd = 1523805520, events = 32586, revents = 0}, {fd = 0, events = 0, revents = 0} <repeats 18 times>, {fd = 1494028800, events = 32586, revents = 0}, {
fd = 74225, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 0,
events = 0, revents = 0}, {fd = 1494028800, events = 32586, revents = 0}, {fd = 15953, events = 0, revents = 0}, {fd = 1494040248, events = 32586,
revents = 0}, {fd = 1494040248, events = 32586, revents = 0}, {fd = 0, events = 0, revents = 0} <repeats 95 times>, {fd = 73393, events = 0,
revents = 0}, {fd = 0, events = 0, revents = 0} <repeats 21 times>, {fd = 73217, events = 0, revents = 0}, {fd = 0, events = 0,
revents = 0} <repeats 13 times>, {fd = 73105, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0} <repeats 23 times>, {fd = 14689, events = 0,
revents = 0}, {fd = 1494042040, events = 32586, revents = 0}, {fd = 1494042040, events = 32586, revents = 0}, {fd = 1523807024, events = 32586,
revents = 0}, {fd = 1523807024, events = 32586, revents = 0}, {fd = 0, events = 0, revents = 0} <repeats 23 times>, {fd = 14465, events = 0,
revents = 0}, {fd = 1494042040, events = 32586, revents = 0}, {fd = 1494042040, events = 32586, revents = 0}, {fd = 1523807248, events = 32586,
revents = 0}, {fd = 1523807248, events = 32586, revents = 0}, {fd = 0, events = 0, revents = 0} <repeats 716 times>}, nfds = 2, end_time = {
tv_sec = 1351610530, tv_usec = 66304}}
(gdb) p seltemp
$4 = (struct select_state *) 0x7f4a5ad38ab8
(gdb) p * seltemp
$5 = {fds = {{fd = 4, events = 1, revents = 1}, {fd = 10, events = 1, revents = 1}, {fd = 11, events = 5, revents = 30068}, {fd = 1702194477, events = 25454,
revents = 25960}, {fd = -1066876818, events = 71, revents = 1}, {fd = 1359020033, events = 128, revents = -31996}, {fd = -1066918212, events = 71,
revents = 28}, {fd = 1359020033, events = 128, revents = 8208}, {fd = 171443713, events = 0, revents = 542}, {fd = -16796891, events = 21022,
revents = -16142}, {fd = 65679, events = 1, revents = 20737}, {fd = -2096889728, events = 956, revents = -16382}, {fd = 65656, events = 1,
revents = 20737}, {fd = -2096889728, events = 3260, revents = -16284}, {fd = 65697, events = 1, revents = 513}, {fd = -2096889814, events = 159,
revents = 1}, {fd = 0, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 0, events = 0,
revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 1634497125, events = 26478, revents = 28261}, {fd = 528, events = 0, revents = 0}, {fd = 80,
events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 4, events = -7348, revents = 0}, {fd = -2132387920, events = 32767, revents = 0}, {
fd = 1496736238, events = 32586, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 1, events = 1, revents = 0}, {fd = 0, events = 0, revents = 0},
{fd = 1, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 74849, events = 0, revents = 0}, {fd = 1523804080, events = 32586,
revents = 0}, {fd = 1143887169, events = 32581, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 48,
events = 0, revents = 0}, {fd = 74801, events = 0, revents = 0}, {fd = 0, events = 32586, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 0,
events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 0, events = 0,
revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 1494028800,
events = 32586, revents = 0}, {fd = 74705, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 1494034560, events = 32586, revents = 0},
{fd = -1, events = 2, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 1523805376, events = 32586, revents = 0},
{fd = -1, events = -1, revents = -1}, {fd = 0, events = 0, revents = 0}, {fd = 1523805392, events = 32586, revents = 0}, {fd = 0, events = 0,
revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = -1, events = 0, revents = 0}, {fd = 0, events = 0,
revents = 0}, {fd = 1523804976, events = 32586, revents = 0}, {fd = 1494029568, events = 32586, revents = 0}, {fd = 0, events = -1, revents = -1}, {
fd = 0, events = 0, revents = 0} <repeats 18 times>, {fd = 16193, events = 0, revents = 0}, {fd = 1494042040, events = 32586, revents = 0}, {
fd = 1494042040, events = 32586, revents = 0}, {fd = 1523805520, events = 32586, revents = 0}, {fd = 1523805520, events = 32586, revents = 0}, {fd = 0,
events = 0, revents = 0} <repeats 18 times>, {fd = 1494028800, events = 32586, revents = 0}, {fd = 74225, events = 0, revents = 0}, {fd = 0,
events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0}, {fd = 1494028800,
events = 32586, revents = 0}, {fd = 15953, events = 0, revents = 0}, {fd = 1494040248, events = 32586, revents = 0}, {fd = 1494040248, events = 32586,
revents = 0}, {fd = 0, events = 0, revents = 0} <repeats 95 times>, {fd = 73393, events = 0, revents = 0}, {fd = 0, events = 0,
revents = 0} <repeats 21 times>, {fd = 73217, events = 0, revents = 0}, {fd = 0, events = 0, revents = 0} <repeats 13 times>, {fd = 73105, events = 0,
revents = 0}, {fd = 0, events = 0, revents = 0} <repeats 23 times>, {fd = 14689, events = 0, revents = 0}, {fd = 1494042040, events = 32586,
revents = 0}, {fd = 1494042040, events = 32586, revents = 0}, {fd = 1523807024, events = 32586, revents = 0}, {fd = 1523807024, events = 32586,
revents = 0}, {fd = 0, events = 0, revents = 0} <repeats 23 times>, {fd = 14465, events = 0, revents = 0}, {fd = 1494042040, events = 32586,
revents = 0}, {fd = 1494042040, events = 32586, revents = 0}, {fd = 1523807248, events = 32586, revents = 0}, {fd = 1523807248, events = 32586,
revents = 0}, {fd = 0, events = 0, revents = 0} <repeats 716 times>}, nfds = 2, end_time = {tv_sec = 1351610530, tv_usec = 66304}}
(gdb) p selret
$6 = 2
(gdb) p * conns
$10 = {fd = -1, err = 22, state = FAILED, is_udp = 0, service = 0x7f4a593581c0 <service_tcp_fd>, socktype = 1, family = 2, addrlen = 16, addr = {
ss_family = 2, __ss_align = 0, __ss_padding = '\000' <repeats 111 times>}, x = {out = {sgbuf = {{iov_base = 0x7f4a5ad3bf54, iov_len = 4}, {
iov_base = 0x7f4a5ad36640, iov_len = 200}}, sgp = 0x7f4a5ad3bf28, sg_count = 2, msg_len_buf = "\000\000", <incomplete sequence \310>}, in = {
bufsizebytes_read = 0, bufsize = 0, buf = 0x0, pos = 0x0, bufsizebytes = "\000\000\000", n_left = 0}}, callback_buffer = {magic = 0, length = 0,
data = 0x0}, server_index = 1, next = 0x0}

Fix spin-loop bug in k5_sendto_kdc

In the second part of the first pass over the server list, we passed
the wrong list pointer to service_fds, causing it to see only a subset
of the server entries corresponding to sel_state. This could cause
service_fds to spin if an event is reported on an fd not in the
subset.

https://github.com/krb5/krb5/commit/2b06a22f7fd8ec01fb27a7335125290b8ceb6f18
Author: Greg Hudson <ghudson@mit.edu>
Commit: 2b06a22f7fd8ec01fb27a7335125290b8ceb6f18
Branch: master
src/lib/krb5/os/sendto_kdc.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)