Am 25.09.26 um 12:57 schrieb Frank Richter:
Am 24.09.26 um 14:48 schrieb Andreas Piesk:
Am 24.09.26 um 13:48 schrieb Frank Richter:
But how to find the cause of the segfault … any hints welcome.
enable core dumps. after a segfault get a backtrace on the dump. binary
should not be stripped, symbols are needed. if you can, compile the code
with debug info.
On Debian 13 with systemd I installed systemd-coredump and dbgsym and src
packages. Then coredumpctl info <pid> shows:
Signal: 11 (SEGV)
Timestamp: Fri 2026-09-25 11:16:18 CEST (1h 21min ago)
Command Line: imapd -U 250
Executable: /usr/lib/cyrus/bin/imapd
…
Message: Process 2916244 (imapd) of user 109 dumped core.
Module libzstd.so.1 from deb libzstd-1.5.7+dfsg-1.amd64
Module libuuid.so.1 from deb
util-linux-2.41.5-0+deb13u1.amd64
Module libgcc_s.so.1 from deb gcc-14-14.2.0-19.amd64
Module libstdc++.so.6 from deb gcc-14-14.2.0-19.amd64
Stack trace of thread 2916244:
#0 0x00007f7c6d27b0b8 prot_vprintf (libcyrus.so.0 + 0x9e0b8)
#1 0x00007f7c6d27b208 prot_printf (libcyrus.so.0 + 0x9e208)
#2 0x000055b50b0fe826 cmd_enable
(/usr/lib/cyrus/bin/imapd + 0x17826)
#3 0x000055b50b119aeb cmdloop (/usr/lib/cyrus/bin/imapd +
0x32aeb)
#4 0x000055b50b11e1cb service_main
(/usr/lib/cyrus/bin/imapd + 0x371cb)
#5 0x000055b50b0f6fac main (/usr/lib/cyrus/bin/imapd +
0xffac)
#6 0x00007f7c6c635ca8 n/a (libc.so.6 + 0x29ca8)
#7 0x00007f7c6c635d65 __libc_start_main (libc.so.6 +
0x29d65)
#8 0x000055b50b0f7631 _start (/usr/lib/cyrus/bin/imapd +
0x10631)
ELF object binary architecture: AMD x86-64
coredumpctl debug <pid> … opens gdb
(gdb) backtrace
#0 0x00007f7c6d27b0b8 in prot_vprintf (s=0x0, fmt=0x55b50b1347dc "%s
ENABLE", pvar=pvar@entry=0x7ffcb5d3d5f0)
at lib/prot.c:1298
#1 0x00007f7c6d27b208 in prot_printf (s=<optimized out>,
fmt=fmt@entry=0x55b50b1347dc "%s ENABLE")
at lib/prot.c:1288
#2 0x000055b50b0fe826 in cmd_enable (tag=0x55b51361fb10 "6") at
imap/imapd.c:14537
#3 0x000055b50b119aeb in cmdloop () at imap/imapd.c:1775
#4 0x000055b50b11e1cb in service_main (argc=<optimized out>,
argv=<optimized out>, envp=envp@entry=0x7ffcb5d404f8)
at imap/imapd.c:1209
#5 0x000055b50b0f6fac in main (argc=<optimized out>, argv=<optimized
out>, envp=0x7ffcb5d404f8)
at master/service.c:647
in prot_vprintf s == NULL!
in prot_printf s == NULL!
in cmd_enable prot_printf(be->out, … be->out is == NULL
(gdb) print *be shows the according backend server (we have a murder),
but out == NULL. So no backend connection?
The client (SOGo webmail) sends: 6 ENABLE QRESYNC
The server runs cyrus-imapd-3.10.3 (self build with Debian patches), 2
frontends, 2 backend servers, 1 mupdate master (on frontend).
Any ideas how to handle this? For me it’s apparently a bug. Shall I open an
issue?
Maybe this helps:
Frontend:
2026-10-09T08:29:11.830162+02:00 sara cyrus/imap[3169994]: starttls: TLSv1.3
with cipher TLS_AES_256_GCM_SHA384 (256/256 bits new) no authentication
2026-10-09T08:29:12.001845+02:00 sara cyrus/imap[3169994]: login:
<webmailserver>.hrz.tu-chemnitz.de [2001:638:911:…] <user> plaintext+TLS
User logged in SESSIONID=<cyrus-1791527351-3169994-1-17718288318570077703>
2026-10-09T08:29:12.048449+02:00 sara cyrus/imap[3169994]: client id
sessionid=<cyrus-1791527351-3169994-1-17718288318570077703> userid=<user>:
"x-originating-ip" "…"
Connecting to backend 1:
2026-10-09T08:29:12.313025+02:00 sara cyrus/imap[3169994]: auditlog: proxy
user sessionid=<cyrus-1791527351-3169994-1-17718288318570077703>
remote=<cyrus-1791527352-456775-1-14270469474560480099>
2026-10-09T08:29:14.749938+02:00 sara cyrus/imap[3169994]: client id
sessionid=<cyrus-1791527351-3169994-1-17718288318570077703> userid=<user>:
"x-originating-ip" "…"
Connecting to backend 2:
2026-10-09T08:29:15.543297+02:00 sara cyrus/imap[3169994]: auditlog: proxy
user sessionid=<cyrus-1791527351-3169994-1-17718288318570077703>
remote=<cyrus-1791527355-312810-1-7932546438329846099>
2026-10-09T08:30:07.064339+02:00 sara cyrus/imap[3169994]: client id
sessionid=<cyrus-1791527351-3169994-1-17718288318570077703> userid=<user>:
"x-originating-ip" "…"
2026-10-09T08:35:14.084474+02:00 sara cyrus/imap[3169994]: client id
sessionid=<cyrus-1791527351-3169994-1-17718288318570077703> userid=<user>:
"x-originating-ip" "…"
… then the client (webmail server) sends the ENABLE QRESYNC, and imapd dies:
segfault core dump:
PID: 3169994 (imapd)
Signal: 11 (SEGV)
Timestamp: Fri 2026-10-09 08:35:14 CEST
Command Line: imapd -U 250
Executable: /usr/lib/cyrus/bin/imapd
Backend 1 = packet: This is where the user’s INBOX is located
2026-10-09T08:29:12.312738+02:00 packet cyrus/imap[456775]: login:
<frontend>.hrz.tu-chemnitz.de [2001:638:911…] user SCRAM-SHA-256 User logged
in SESSIONID=<cyrus-1791527352-456775-1-14270469474560480099>
2026-10-09T08:35:14.393819+02:00 packet cyrus/imap[456775]: session ended:
sessionid=<cyrus-1791527352-456775-1-14270469474560480099> userid=<user>
id.name=<(null)> condstore=<1> qresync=<1>
Backend 2 = parcel: with a shared mailbox the user has access to
2026-10-09T08:29:15.542749+02:00 parcel cyrus/imap[312810]: login:
<frontend>.hrz.tu-chemnitz.de [2001:638:911…] user SCRAM-SHA-256 User logged
in SESSIONID=<cyrus-1791527355-312810-1-7932546438329846099>
2026-10-09T08:34:15.359427+02:00 parcel cyrus/imap[312810]: session ended:
sessionid=<cyrus-1791527355-312810-1-7932546438329846099> userid=<user>
id.name=<(null)>
… this connection was closed!
code in imap/imapd.c
14532 if (ptrarray_size(&backend_cached)) {
14533 /* ENABLE on all remote mailboxes */
14534 for (int i = 0; i < ptrarray_size(&backend_cached); i++) {
14535 struct backend *be = ptrarray_nth(&backend_cached, i);
14536
14537 prot_printf(be->out, "%s ENABLE", tag);
(gdb) print *be
$1 = {hostname = "parcel.…", '\000' <repeats 38 times>,
banner = "* OK [CAPABILITY IMAP4rev1 IMAP4rev2 AUTH=SCRAM-SHA-256 ENABLE
ID LITERAL+ LOGINDISABLED SASL-IR STARTTLS MUPDATE=mupdate:/…/] parcel.…
Cyrus IMAP 3.10.3-Deb"..., addr = {ss_family = 10,
__ss_padding = "\000\217\000\000\000\000
\001\0068\t\021\v\016\0014\001\t\002(\002U", '\000' <repeats 95 times>,
__ss_align = 0}, sock = -1,
prot = 0x5612f3a4f020 <imap_protocol>, context = 0x0, clientin = 0x0,
current = 0x0, inbox = 0x0, timeout = 0x0, saslconn = 0x0, sasl_cb = 0x0,
ext_ssf = 0, tlsconn = 0x0, tlssess = 0x0, capability = 0, num_cap_params
= 0, cap_params = 0x0, last_result = {s = 0x0, len = 0, alloc = 0,
flags = 0}, in = 0x0, *out = 0x0*}
Thanks,
Frank
--
Frank Richter, Chemnitz University of Technology, Germany
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