(gdb) bt
#0  __pthread_kill_implementation (threadid=<optimized out>, signo=signo@entry=6, no_tid=no_tid@entry=0)
    at pthread_kill.c:44
#1  0x00007fae912a15b3 in __pthread_kill_internal (signo=6, threadid=<optimized out>) at pthread_kill.c:78
#2  0x00007fae91254d06 in __GI_raise (sig=sig@entry=6) at ../sysdeps/posix/raise.c:26
#3  0x00007fae912287f3 in __GI_abort () at abort.c:79
#4  0x00007fae91687da0 in log_assert_failed (text=<optimized out>, file=<optimized out>, line=<optimized out>, 
    func=<optimized out>) at ../src/basic/log.c:853
#5  0x00007fae917c14e7 in connect_unix_path (fd=4, dir_fd=-1, path=0x556d5cc6bf70 "/run/repro.socket")
    at ../src/basic/socket-util.c:1437
#6  0x00007fae91794a02 in read_full_file_full (dir_fd=dir_fd@entry=-1, filename=0x556d5cc6bf70 "/run/repro.socket", 
    offset=offset@entry=18446744073709551615, size=size@entry=1048576, 
    flags=flags@entry=(READ_FULL_FILE_SECURE | READ_FULL_FILE_CONNECT_SOCKET | READ_FULL_FILE_FAIL_WHEN_LARGER), 
    bind_name=<optimized out>, ret_contents=0x7ffd71011e30, ret_size=0x7ffd71011e20) at ../src/basic/fileio.c:798
#7  0x00007fae91aa51f4 in load_credential (context=0x556d5cdc6b98, params=<optimized out>, id=0x556d5cdf6c90 "foo", 
    path=0x556d5cc6bf70 "/run/repro.socket", encrypted=<optimized out>, unit=<optimized out>, read_dfd=-1, 
    write_dfd=3, uid=4294967295, ownership_ok=true, left=0x7ffd71011f30) at ../src/core/execute.c:2734
#8  0x00007fae91aa59c3 in acquire_credentials (ownership_ok=true, uid=4294967295, p=<optimized out>, 
    unit=0x556d5ccd4930 "reproducer.service", params=0x7ffd71012580, context=0x556d5cdc6b98)
    at ../src/core/execute.c:2884
 :
(gdb) f 5
#5  0x00007fae917c14e7 in connect_unix_path (fd=4, dir_fd=-1, path=0x556d5cc6bf70 "/run/repro.socket")
    at ../src/basic/socket-util.c:1437
1437	        assert(dir_fd == AT_FDCWD || dir_fd >= 0);
(gdb) p dir_fd
$1 = -1
(gdb) up
#6  0x00007fae91794a02 in read_full_file_full (dir_fd=dir_fd@entry=-1, filename=0x556d5cc6bf70 "/run/repro.socket", 
    offset=offset@entry=18446744073709551615, size=size@entry=1048576, 
    flags=flags@entry=(READ_FULL_FILE_SECURE | READ_FULL_FILE_CONNECT_SOCKET | READ_FULL_FILE_FAIL_WHEN_LARGER), 
    bind_name=<optimized out>, ret_contents=0x7ffd71011e30, ret_size=0x7ffd71011e20) at ../src/basic/fileio.c:798
798	                r = connect_unix_path(sk, dir_fd, filename);
(gdb) 
#7  0x00007fae91aa51f4 in load_credential (context=0x556d5cdc6b98, params=<optimized out>, id=0x556d5cdf6c90 "foo", 
    path=0x556d5cc6bf70 "/run/repro.socket", encrypted=<optimized out>, unit=<optimized out>, read_dfd=-1, 
    write_dfd=3, uid=4294967295, ownership_ok=true, left=0x7ffd71011f30) at ../src/core/execute.c:2734
2734	                r = read_full_file_full(
(gdb) 
#8  0x00007fae91aa59c3 in acquire_credentials (ownership_ok=true, uid=4294967295, p=<optimized out>, 
    unit=0x556d5ccd4930 "reproducer.service", params=0x7ffd71012580, context=0x556d5cdc6b98)
    at ../src/core/execute.c:2884
2884	                        r = load_credential(
(gdb) list
2879	                                return log_debug_errno(errno, "Failed to open '%s': %m", lc->path);
2880	                }
2881	
2882	                if (sub_fd < 0)
2883	                        /* Regular file (incl. a credential passed in from higher up) */
2884	                        r = load_credential(
2885	                                        context,
2886	                                        params,
2887	                                        lc->id,
2888	                                        lc->path,
(gdb) 
2889	                                        lc->encrypted,
2890	                                        unit,
2891	                                        -1,
2892	                                        dfd,
2893	                                        uid,
2894	                                        ownership_ok,
2895	                                        &left);
2896	                else
2897	                        /* Directory */
2898	                        r = recurse_dir(
 :

commit 661e4251a5b157d1aee1df98fbd2f0c95285ebba
Author: Daan De Meyer <daan.j.demeyer@gmail.com>
Date:   Tue Dec 13 10:50:01 2022 +0000

    execute: Pass AT_FDCWD instead of -1
    
    Let's enforce that callers pass AT_FDCWD as read_dfd to load_credential()
    to avoid an assert() in read_full_file_full() if read_dfd is -1.

Apr 04 15:20:31 vm-rhel9 systemd[1]: Starting reproducer.service...
Apr 04 15:20:31 vm-rhel9 systemd[39710]: Assertion 'dir_fd == AT_FDCWD || dir_fd >= 0' failed at src/basic/socket-util.c:1437, function connect_unix_path(). Aborting.