Dear David,

I managed to reproducibly crash nullmailer-smtpd with a "general
protection fault" by calling the following command:

  swaks -t abe@debian.org --pipe 'sendmail -bs'

This call produces the following output first:

  === Trying pipe to sendmail -bs...
  === Connected to sendmail -bs.
  <-  220 nullmailer-smtpd ready
   -> EHLO kote1.lugs.ch
  <-  250 2.3.0 OK
   -> MAIL FROM:<root@kote1.lugs.ch>
  <-  250 2.1.0 Sender accepted
   -> RCPT TO:<abe@debian.org>
  <-  250 2.1.5 Recipient accepted
   -> DATA
  <-  354 End your message with a period on a line by itself
   -> Date: Mon, 10 Jun 2024 13:21:49 +0200
   -> To: abe@debian.org
   -> From: root@kote1.lugs.ch
   -> Subject: test Mon, 10 Jun 2024 13:21:49 +0200
   -> Message-Id: <20240610132149.015058@kote1.lugs.ch>
   -> X-Mailer: swaks v20240103.0 jetmore.org/john/code/swaks/
   ->
   -> This is a test mailing
   ->
   ->
   -> .
  *** Child process closed connection unexpectedly.

In /var/log/syslog I then find these log entries:

  2024-06-10T13:21:49.468475+02:00 kote1 nullmailer: Trigger pulled.
  2024-06-10T13:21:49.468687+02:00 kote1 nullmailer: Rescanning queue.
  2024-06-10T13:21:49.468781+02:00 kote1 nullmailer: Starting delivery, 1 message(s) in queue.
  2024-06-10T13:21:49.468793+02:00 kote1 nullmailer: Starting delivery: host: … protocol: smtp file: 1718018509.15060
  2024-06-10T13:21:49.468802+02:00 kote1 nullmailer: From: <root@kote1.lugs.ch> to: <abe@debian.org>
  2024-06-10T13:21:49.468808+02:00 kote1 nullmailer: Message-Id: <20240610132149.015058@kote1.lugs.ch>
  2024-06-10T13:21:49.471688+02:00 kote1 kernel: traps: nullmailer-smtp[15059] general protection fault ip:7f0368d73dd9 sp:7fff5e3d7088 error:0 in libc.so.6[7f0368c41000+157000]
  2024-06-10T13:21:49.600127+02:00 kote1 nullmailer: smtp: Succeeded: 250 2.6.0 <20240610132149.015058@kote1.lugs.ch> [InternalId=172490181574991, Hostname=…] 1171 bytes in 0.106, 10.754 KB/sec Queued mail for delivery
  2024-06-10T13:21:49.601067+02:00 kote1 nullmailer: Sent file.
  2024-06-10T13:21:49.601118+02:00 kote1 nullmailer: Delivery complete, 0 message(s) remain.

The mail though seemed to end up in the queue. But since swaks exits
with non-zero due to "sendmail -bs" exits with non-zero, our Ansible
playbook fails, too.

I initially ran into this on a production host running Debian 11
Bullseye with different settings (hence marking as found in the version
in Bullseye), but I can still reproduce it on a test VM with Debian
Unstable where I installed nullmailer temporarily as well. (Bug report
resembles state on the latter.)

Axel Beckert <abe@debian.org> writes:

I can duplicate this. I made a few (unsuccessful) attempts at localize
the error.

Attempt #1

If I run /usr/lib/sendmail -bs directly (or nullmailer-smtpd, which
amounts to the same thing, I think), and give exactly the same input, it
exits cleanly when I type QUIT.  I also tried your swaks command on a
host where sendmail is postfix, and I see end of the transaction

    -> .
    <-  250 2.0.0 Ok: queued as 5EC225FB72
     -> QUIT
    <-  221 2.0.0 Bye
    === Connection closed with child process.

Attempt #2

swaks -t bremner@debian.org --pipe 'gdb -batch -ex run -ex bt --args /usr/lib/sendmail -bs'

This actually runs without segfaulting, which made me think it might be
a memory error.

Attempt #3

swaks -t bremner@debian.org --pipe 'valgrind /usr/lib/sendmail -bs'

This also runs without errors, so I'm out of ideas for the moment.

Hi David,

David Bremner wrote:
https://github.com/bruceg/nullmailer/commit/834e2eb6b7eac2648fc371c432a46e98d5966bb4

Could it be this one? At least "fdbuf.c" sounds as if it might be
involved in file descriptor thingies.

Clearly a Heisenbug. ;-)

Maybe upstream has an idea if it's not that already made commit?

		Regards, Axel

Axel Beckert <abe@debian.org> writes:

We're actually running a snapshot of master, so that commit is in
testing and unstable.

d

David Bremner <david@tethera.net> writes:

Attempt #4:

Rebuild with asan

make clean
make CXXFLAGS="-g -O1 -fsanitize=address"
make check

I don't know if this is coincidence, or actually meaningful, but the
test "Testing protocol success with smtp (stdin)" finds one memory leak.

    220 OK
    smtp: Succeeded: 220 OK

    =================================================================
    ==3035435==ERROR: LeakSanitizer: detected memory leaks

    Direct leak of 13 byte(s) in 1 object(s) allocated from:
        #0 0x7f64762edd10 in strdup ../../../../src/libsanitizer/asan/asan_interceptors.cpp:578
        #1 0x563a16835173 in parse_option /home/bremner/software/debian/nullmailer/protocols/protocol.cc:116
        #2 0x563a16835173 in parse_options /home/bremner/software/debian/nullmailer/protocols/protocol.cc:130
        #3 0x563a16835173 in cli_main(int, char**) /home/bremner/software/debian/nullmailer/protocols/protocol.cc:138

    SUMMARY: AddressSanitizer: 13 byte(s) leaked in 1 allocation(s).

Looking at the code there is indeed a leak, but it's hard to see how it
would lead to a crash.

Hello David, hello Axel,
I tried if I can reproduce it and if rr-debugger might be able to record it.

And I received following replay session of the crashing process (PID 3025:

- It forks another process nullmailer-queue (in this example PID 3026)

- It calls waitpid on the PID 3026, but this returns -1 and errno=10 (seems to be ECHILD)
   for some unknown reason.

- Therefore tries to write a error message, but the content and the pointer to cli_program
   seem to get mixed up, therefore the strlen crashes.

Especially the third point is puzzling, I could not yet see why this pointer-content-mixup happens.

Kind regards,
Bernhard




root@debian:~# rr replay --debugger-option=-q -p 3025 -g 2000 bash-1
root@debian:~# swaks -t abe@debian.org --pipe 'sendmail -bs'
=== Trying pipe to sendmail -bs...
=== Connected to sendmail -bs.
Reading symbols from /root/.local/share/rr/bash-1/mmap_pack_11_nullmailer-smtpd...
Reading symbols from /usr/lib/debug/.build-id/42/8c5f859ee211c1dfa8accdc66572493c471db1.debug...
Really redefine built-in command "restart"? (y or n) [answered Y; input not from terminal]
Really redefine built-in command "jump"? (y or n) [answered Y; input not from terminal]
Remote debugging using 127.0.0.1:7992

--------------------------------------------------
  ---> Reached target process 3025 at event 2000.
--------------------------------------------------
Reading symbols from /usr/bin/../lib/rr/librrpreload.so...
Reading symbols from /lib/x86_64-linux-gnu/libdl.so.2...
Reading symbols from /usr/lib/debug/.build-id/bc/40b1b7b2a76bc40d2372f4036be41bef33ef14.debug...
Reading symbols from /lib/x86_64-linux-gnu/libstdc++.so.6...
(No debugging symbols found in /lib/x86_64-linux-gnu/libstdc++.so.6)
Reading symbols from /lib/x86_64-linux-gnu/libc.so.6...
Reading symbols from /usr/lib/debug/.build-id/2e/01923fea4ad9f7fa50fe24e0f3385a45a6cd1c.debug...
Reading symbols from /lib/x86_64-linux-gnu/libm.so.6...
Reading symbols from /usr/lib/debug/.build-id/6c/771bfaca294a4e3d85ada43b358bf6b49dcd2a.debug...
Reading symbols from /lib64/ld-linux-x86-64.so.2...
Reading symbols from /usr/lib/debug/.build-id/a9/700083811ae36d1017fe16ebe5657d59cdda0a.debug...
Reading symbols from /lib/x86_64-linux-gnu/libgcc_s.so.1...
(No debugging symbols found in /lib/x86_64-linux-gnu/libgcc_s.so.1)
BFD: warning: system-supplied DSO at 0x6fffd000 has a section extending past end of file
0x00007f0527d7f8b7 in __GI_mprotect () at ../sysdeps/unix/syscall-template.S:117
117     ../sysdeps/unix/syscall-template.S: Datei oder Verzeichnis nicht gefunden.
(rr) set width 0
(rr) set pagination off
(rr) directory /home/benutzer/source/nullmailer/orig/nullmailer-2.2+10~g7ed88a0/lib
Source directories searched: /home/benutzer/source/nullmailer/orig/nullmailer-2.2+10~g7ed88a0/lib:$cdir:$cwd
(rr) directory /home/benutzer/source/nullmailer/orig/nullmailer-2.2+10~g7ed88a0/src
Source directories searched: /home/benutzer/source/nullmailer/orig/nullmailer-2.2+10~g7ed88a0/src:/home/benutzer/source/nullmailer/orig/nullmailer-2.2+10~g7ed88a0/lib:$cdir:$cwd
(rr) display/i $pc
1: x/i $pc
=> 0x7f0527d7f8b7 <__GI_mprotect+7>:    cmp    $0xfffffffffffff001,%rax
(rr) b fork
Breakpoint 1 at 0x7f05278f5560: file ./posix/fork.c, line 41.
(rr) cont
Continuing.
<-  220 nullmailer-smtpd ready
  -> EHLO debian
<-  250 2.3.0 OK
  -> MAIL FROM:<root@debian>
<-  250 2.1.0 Sender accepted
  -> RCPT TO:<abe@debian.org>
<-  250 2.1.5 Recipient accepted
  -> DATA

Breakpoint 1, __libc_fork () at ./posix/fork.c:41
41      ./posix/fork.c: Datei oder Verzeichnis nicht gefunden.
1: x/i $pc
=> 0x7f05278f5560 <__libc_fork>:        push   %r14
(rr) finish
Run till exit from #0  __libc_fork () at ./posix/fork.c:41
0x00005639bd9132d5 in fork_exec::start (this=this@entry=0x7ffc4099cd00, args=args@entry=0x7ffc4099cca0, redirn=redirn@entry=3, redirs=redirs@entry=0x7ffc4099cc90) at ./lib/forkexec.cc:67
67        if ((pid = fork()) < 0)
1: x/i $pc
=> 0x5639bd9132d5 <_ZN9fork_exec5startEPPKciPi+501>:    mov    -0x58(%rbp),%rsi
Value returned is $1 = 3026
(rr) next
69        if (pid == 0) {
1: x/i $pc
=> 0x5639bd9132e3 <_ZN9fork_exec5startEPPKciPi+515>:    jne    0x5639bd913306 <_ZN9fork_exec5startEPPKciPi+550>
(rr) print pid
$2 = 3026
(rr) b fork_exec::wait
Breakpoint 2 at 0x5639bd912ea0: file ./lib/forkexec.cc, line 121.
(rr) cont
Continuing.
<-  354 End your message with a period on a line by itself
  -> Date: Fri, 21 Jun 2024 00:10:45 +0200
  -> To: abe@debian.org
  -> From: root@debian
  -> Subject: test Fri, 21 Jun 2024 00:10:45 +0200
  -> Message-Id: <20240621001045.003024@debian>
  -> X-Mailer: swaks v20240103.0 jetmore.org/john/code/swaks/
  ->
  -> This is a test mailing
  ->
  ->
  -> .

Breakpoint 2, fork_exec::wait (this=this@entry=0x7ffc4099cd00) at ./lib/forkexec.cc:121
121     {
1: x/i $pc
=> 0x5639bd912ea0 <_ZN9fork_exec4waitEv>:       endbr64
(rr) next
122       if (pid > 0) {
1: x/i $pc
=> 0x5639bd912ec1 <_ZN9fork_exec4waitEv+33>:    test   %edi,%edi
(rr)
123         int status = wait_status();
1: x/i $pc
=> 0x5639bd912ef0 <_ZN9fork_exec4waitEv+80>:    xor    %edx,%edx
(rr) step
fork_exec::wait_status (this=0x7ffc4099cd00) at ./lib/forkexec.cc:112
112         if (waitpid(pid, &status, 0) == pid) {
1: x/i $pc
=> 0x5639bd912ef0 <_ZN9fork_exec4waitEv+80>:    xor    %edx,%edx
(rr) stepi
0x00005639bd912ef2      112         if (waitpid(pid, &status, 0) == pid) {
1: x/i $pc
=> 0x5639bd912ef2 <_ZN9fork_exec4waitEv+82>:    lea    0x4(%rsp),%rsi
(rr)
0x00005639bd912ef7      112         if (waitpid(pid, &status, 0) == pid) {
1: x/i $pc
=> 0x5639bd912ef7 <_ZN9fork_exec4waitEv+87>:    call   0x5639bd9110f0 <waitpid@plt>
(rr)
0x00005639bd9110f0 in waitpid@plt ()
1: x/i $pc
=> 0x5639bd9110f0 <waitpid@plt>:        jmp    *0x6e4a(%rip)        # 0x5639bd917f40 <waitpid@got.plt>
(rr)
__GI___waitpid (pid=3026, stat_loc=0x7ffc4099ccb4, options=0) at ./posix/waitpid.c:38
38      ./posix/waitpid.c: Datei oder Verzeichnis nicht gefunden.
1: x/i $pc
=> 0x7f05279109e0 <__GI___waitpid>:     xor    %ecx,%ecx
(rr) finish
Run till exit from #0  __GI___waitpid (pid=3026, stat_loc=0x7ffc4099ccb4, options=0) at ./posix/waitpid.c:38
0x00005639bd912efc in fork_exec::wait_status (this=0x7ffc4099cd00) at ./lib/forkexec.cc:112
112         if (waitpid(pid, &status, 0) == pid) {
1: x/i $pc
=> 0x5639bd912efc <_ZN9fork_exec4waitEv+92>:    cmp    (%rbx),%eax
Value returned is $3 = -1
(rr) print status
$4 = 0
(rr) print errno
$5 = 10
(rr) stepi
0x00005639bd912efe      112         if (waitpid(pid, &status, 0) == pid) {
1: x/i $pc
=> 0x5639bd912efe <_ZN9fork_exec4waitEv+94>:    jne    0x5639bd913058 <_ZN9fork_exec4waitEv+440>
(rr)
0x00005639bd913058 in fork_exec::wait (this=this@entry=0x7ffc4099cd00) at ./lib/forkexec.cc:134
134           FAIL(name << " crashed or was killed");
1: x/i $pc
=> 0x5639bd913058 <_ZN9fork_exec4waitEv+440>:   mov    0x20e1(%rip),%rbp        # 0x5639bd915140 <cli_program>
(rr) x/2xg $rip + 0x20e1
0x5639bd915139: 0x6e00000000000000      0x656c69616d6c6c75
(rr) print cli_program
$6 = "nullmailer-smtpd"
(rr) stepi
fdobuf::operator<< (str=<optimized out>, this=<optimized out>) at ./fdbuf/fdobuf.h:59
59            write(str, strlen(str));
1: x/i $pc
=> 0x5639bd91305f <_ZN9fork_exec4waitEv+447>:   lea    0x201f(%rip),%r12        # 0x5639bd915085
(rr)
0x00005639bd913066 in fdobuf::operator<< (str=0x6c69616d6c6c756e <error: Cannot access memory at address 0x6c69616d6c6c756e>, this=<optimized out>) at ./fdbuf/fdobuf.h:59
59            write(str, strlen(str));
1: x/i $pc
=> 0x5639bd913066 <_ZN9fork_exec4waitEv+454>:   mov    %rbp,%rdi
(rr)
0x00005639bd913069      59            write(str, strlen(str));
1: x/i $pc
=> 0x5639bd913069 <_ZN9fork_exec4waitEv+457>:   call   0x5639bd9110a0 <strlen@plt>
(rr)
0x00005639bd9110a0 in strlen@plt ()
1: x/i $pc
=> 0x5639bd9110a0 <strlen@plt>: jmp    *0x6e72(%rip)        # 0x5639bd917f18 <strlen@got.plt>
(rr)
__strlen_avx2 () at ../sysdeps/x86_64/multiarch/strlen-avx2.S:65
65      ../sysdeps/x86_64/multiarch/strlen-avx2.S: Datei oder Verzeichnis nicht gefunden.
1: x/i $pc
=> 0x7f0527973dc0 <__strlen_avx2>:      mov    %edi,%eax
(rr) finish
Run till exit from #0  __strlen_avx2 () at ../sysdeps/x86_64/multiarch/strlen-avx2.S:65

Program received signal SIGSEGV, Segmentation fault.
__strlen_avx2 () at ../sysdeps/x86_64/multiarch/strlen-avx2.S:76
76      in ../sysdeps/x86_64/multiarch/strlen-avx2.S
1: x/i $pc
=> 0x7f0527973dd9 <__strlen_avx2+25>:   vpcmpeqb (%rdi),%ymm0,%ymm1
(rr) bt
#0  __strlen_avx2 () at ../sysdeps/x86_64/multiarch/strlen-avx2.S:76
#1  0x00005639bd91306e in fdobuf::operator<< (str=0x6c69616d6c6c756e <error: Cannot access memory at address 0x6c69616d6c6c756e>, this=<optimized out>) at ./fdbuf/fdobuf.h:59
#2  fork_exec::wait (this=this@entry=0x7ffc4099cd00) at ./lib/forkexec.cc:125
#3  0x00005639bd91201f in DATA (param=...) at ./src/smtpd.cc:159
#4  DATA (param=...) at ./src/smtpd.cc:127
#5  0x00005639bd91144f in dispatch () at ./src/smtpd.cc:252
#6  main () at ./src/smtpd.cc:263
(rr) list 34
34
35      #define ERR(MSG) do{ ferr << cli_program << ": " << MSG << ": " << strerror(errno) << endl; } while(0)
36      #define FAIL(MSG) do{ ERR(MSG); return false; }while(0)
37
(rr) list fork_exec::wait
119
120     bool fork_exec::wait()
121     {
122       if (pid > 0) {
123         int status = wait_status();
124         if (status < 0)
125           FAIL("Error catching the return value from " << name);
126         if (WIFEXITED(status)) {
127           status = WEXITSTATUS(status);
128           if (status) {
129             ferr << cli_program << ": " << name << " failed: " << status << endl;
130             return false;
131           }
132         }
133         else
134           FAIL(name << " crashed or was killed");
135       }
136       return true;
137     }
(rr)

Am 21.06.24 um 01:57 schrieb Bernhard Übelacker:


Hello David, hello Axel,
I did some further tests and found following location where cli_program
is delared here:

   ./lib/cli++/cli++.h:35:extern const char* cli_program;

But the defintion looks a bit different:

   ./src/smtpd.cc:55:extern const char cli_program[] = "nullmailer-smtpd";


A package built with following change does no longer show this crash.

Kind regards,
Bernhard

--- src/smtpd.cc.orig   2023-04-22 19:06:36.000000000 +0200
+++ src/smtpd.cc        2024-06-21 10:45:25.982395298 +0200
@@ -53,5 +53,5 @@ static mystring sender;
  static mystring recipients;

Bernhard Übelacker <bernhardu@mailbox.org> writes:

Hi Bernhard;

Thanks for the patch. This does seem to be progress, but I don't think
it completely fixes Axel's bug. At least for me I still see

 -> .
nullmailer-smtpd: Error catching the return value from nullmailer-queue: No child processes
nullmailer-smtpd: Error catching the return value from nullmailer-queue: No child processes
<** 451 4.3.0 Error returned from nullmailer-queue

and I get a non-zero exit code. I think the problem you found was
probably a crash during the reporting of the error message.

Am 21.06.24 um 20:47 schrieb David Bremner:

Yes, it was crashing while it tried to write the error message.

I had hoped the expected behaviour might have been the error message ;-)

I did some archaeology and found the issue got visible
at 2017-12-30 in the Buster development cycle with the
migration of nullmailer 1:2.1-5 into testing.


Kind regards,
Bernhard



debian-9-stretch:                                                     Connection closed with child process.
testing https://snapshot.debian.org/archive/debian/20170801T042817Z/: Connection closed with child process.
testing https://snapshot.debian.org/archive/debian/20170901T034632Z/: Connection closed with child process.
testing https://snapshot.debian.org/archive/debian/20171001T043059Z/: Connection closed with child process.
testing https://snapshot.debian.org/archive/debian/20171101T034619Z/: Connection closed with child process.
testing https://snapshot.debian.org/archive/debian/20171201T034339Z/: Connection closed with child process.
testing https://snapshot.debian.org/archive/debian/20171215T032758Z/: Connection closed with child process.
testing https://snapshot.debian.org/archive/debian/20171223T034540Z/: Connection closed with child process.
testing https://snapshot.debian.org/archive/debian/20171227T051715Z/: Connection closed with child process.
testing https://snapshot.debian.org/archive/debian/20171229T045928Z/: Connection closed with child process.
testing https://snapshot.debian.org/archive/debian/20171230T035716Z/: Child process closed connection unexpectedly. nullmailer (1:2.1-5) over (1:1.13-1.2) ...
testing https://snapshot.debian.org/archive/debian/20180101T053014Z/: Child process closed connection unexpectedly.
debian-10-buster:                                                     Child process closed connection unexpectedly.
debian-11-bullseye:                                                   Child process closed connection unexpectedly.
debian-12-bookworm:                                                   Child process closed connection unexpectedly.

Am 22.06.24 um 00:42 schrieb Bernhard Übelacker:
Hello,
trying to go more into detail a git bisect
shows following upstream commit [1].

Kind regards,
Bernhard


https://snapshot.debian.org/package/nullmailer/1%3A1.13-1.2/:         Connection closed with child process.
git checkout 1.13:                                                    Connection closed with child process.
1.13-68-g2e30750:                                                     Connection closed with child process.
1.13-69-g5850a49:                                                     Child process closed connection unexpectedly.
git checkout 2.0:                                                     Child process closed connection unexpectedly.
https://snapshot.debian.org/package/nullmailer/1%3A2.0-1/:            Child process closed connection unexpectedly.


5850a49ade78d36ce33d70c28198b9cf2fb8fbdd is the first broken commit
commit 5850a49ade78d36ce33d70c28198b9cf2fb8fbdd
Author: Bruce Guenter <bruce@untroubled.org>
Date:   Fri Jan 15 11:40:38 2016 -0600

     lib: Add fork_exec wrapper class for launching sub-programs

  lib/Makefile.am |   1 +
  lib/autoclose.h |   7 ++-
  lib/forkexec.cc | 136 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  lib/forkexec.h  |  32 +++++++++++++
  src/inject.cc   | 108 +++++++++++++-------------------------------
  src/send.cc     |   1 +
  src/smtpd.cc    |  63 +++++---------------------
  7 files changed, 217 insertions(+), 131 deletions(-)
  create mode 100644 lib/forkexec.cc
  create mode 100644 lib/forkexec.h


[1] https://github.com/bruceg/nullmailer/commit/5850a49ade78d36ce33d70c28198b9cf2fb8fbdd

Hello David, hello Axel,

Maybe it is the expected behaviour?

Following is the output of the last not crashing version 1.13
and the current version in testing 2.2+10~g7ed88a0 with the cli_program fix.

Both look quite similar except the previously crashing error message,
so this is maybe expected by upstream?

Kind regards,
Bernhard


1.13-1.2                                                          ||  2.2+10~g7ed88a0-5  +  const char* cli_program = "nullmailer-smtpd";
                                                                   ||
root@debian:~# swaks -t abe@debian.org --pipe 'sendmail -bs'      ||  root@debian:~# swaks -t abe@debian.org --pipe 'sendmail -bs'
=== Trying pipe to sendmail -bs...                                ||  === Trying pipe to sendmail -bs...
=== Connected to sendmail -bs.                                    ||  === Connected to sendmail -bs.
<-  220 nullmailer-smtpd ready                                    ||  <-  220 nullmailer-smtpd ready
  -> EHLO debian                                                   ||   -> EHLO debian
<-  250 2.3.0 OK                                                  ||  <-  250 2.3.0 OK
  -> MAIL FROM:<root@debian>                                       ||   -> MAIL FROM:<root@debian>
<-  250 2.1.0 Sender accepted                                     ||  <-  250 2.1.0 Sender accepted
  -> RCPT TO:<abe@debian.org>                                      ||   -> RCPT TO:<abe@debian.org>
<-  250 2.1.5 Recipient accepted                                  ||  <-  250 2.1.5 Recipient accepted
  -> DATA                                                          ||   -> DATA
<-  354 End your message with a period on a line by itself        ||  <-  354 End your message with a period on a line by itself
  -> Date: Sun, 23 Jun 2024 00:xx:xx +0200                         ||   -> Date: Sun, 23 Jun 2024 00:xx:xx +0200
  -> To: abe@debian.org                                            ||   -> To: abe@debian.org
  -> From: root@debian                                             ||   -> From: root@debian
  -> Subject: test Sun, 23 Jun 2024 00:xx:xx +0200                 ||   -> Subject: test Sun, 23 Jun 2024 00:xx:xx +0200
  -> Message-Id: <2024062300xxxx.0xxxxx@debian>                    ||   -> Message-Id: <2024062300xxxx.0xxxxx@debian>
  -> X-Mailer: swaks v20170101.0 jetmore.org/john/code/swaks/      ||   -> X-Mailer: swaks v20240103.0 jetmore.org/john/code/swaks/
  ->                                                               ||   ->
  -> This is a test mailing                                        ||   -> This is a test mailing
  ->                                                               ||   ->
                                                                   ||   ->
  -> .                                                             ||   -> .
                                                                   ||  nullmailer-smtpd: Error catching the return value from nullmailer-queue: No child processes
                                                                   ||  nullmailer-smtpd: Error catching the return value from nullmailer-queue: No child processes
<** 451 4.3.0 Error checking return status from nullmailer-queue  ||  <** 451 4.3.0 Error returned from nullmailer-queue
  -> QUIT                                                          ||   -> QUIT
<-  221 2.0.0 Good bye                                            ||  <-  221 2.0.0 Good bye
=== Connection closed with child process.                         ||  === Connection closed with child process.
root@debian:~#                                                    ||  root@debian:~#

Bernhard Übelacker <bernhardu@mailbox.org> writes:

Or it's just an old bug?

It still looks like pretty strange behaviour to me. Does (nullmailer's
version of) sendmail -bs always return a non-zero exit code, or just in
some circumstances?

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Es gibt eine Familienspende in Höhe von 1.850.000,00 USD von Cheng Charlie
Saephan. Bitte antworten Sie für weitere Informationen. Denken Sie daran,
Ihrer Familie und den Bedürftigen in Ihrer Umgebung Gutes zu tun.

Dies ist bereits der zweite Versuch, Sie zu erreichen. Bitte antworten Sie
für weitere Details.