Re: sshd-session (sshd on conect) crashes with signal 6

On Fri, 15 Aug 2025 14:06:20 +0200,
Henryk Paluch <henryk.paluch@pickering.cz> wrote:
> 
> Hello!
> 
> After one week following current I recently started experiencing
> sshd-session crashes on 2 machines running latest 15.0-PRERELEASE (git Main branch).
> 
> Anytime I try to SSH login to my 15.0-PRERELASE, sshd crashes on  sshd-sesson subprocess with:
> 
> pid 1217 (sshd-session), jid 0, uid 0: exited on signal 6
> 
> More details:
> 
> gdb /usr/libexec/sshd-session  /sshd-session.core
> 
> Core was generated by `sshd-session: ansible [priv]'.                                                                      
> Program terminated with signal SIGABRT, Aborted.                                                                           
> Sent by thr_kill() from pid 15843 and user 0.                                                                              
> #0  thr_kill () at thr_kill.S:4                                                                                                                                                                                                                       
> warning: Source file is more recent than executable.
> 4       RSYSCALL(thr_kill)                                   
> (gdb) bt                                                                                                                   
> #0  thr_kill () at thr_kill.S:4
> #1  0x000019ceda634fa4 in __raise (s=s@entry=6) at /usr/src/lib/libc/gen/raise.c:48
> #2  0x000019ceda6e52a9 in abort () at /usr/src/lib/libc/stdlib/abort.c:61
> #3  0x000019ceda617d51 in __assert (func=<optimized out>, file=<optimized out>, line=line@entry=134, 
>     failedexpr=<optimized out>) at /usr/src/lib/libc/gen/assert.c:47
> #4  0x000019c6b21029c3 in temporarily_use_uid (pw=pw@entry=0x3c3261215280) at /usr/src/crypto/openssh/uidswap.c:134
> #5  0x000019c6b20e8517 in user_key_allowed2 (pw=0x3c3261215280, key=0x3c32612e5820, 
>     file=0x3c3261233e30 "/home/ansible/.ssh/authorized_keys", remote_ip=0x3c3261212da0 "192.168.122.1", 
>     remote_host=0x3c3261212dd0 "192.168.122.1", authoptsp=0x19ced2ed0590) at /usr/src/crypto/openssh/auth2-pubkey.c:599
> #6  user_key_allowed (ssh=ssh@entry=0x3c32612f4000, pw=0x3c3261215280, key=0x3c32612e5820, auth_attempt=<optimized out>, 
>     authoptsp=authoptsp@entry=0x19ced2ed0688) at /usr/src/crypto/openssh/auth2-pubkey.c:783
> #7  0x000019c6b20ed99d in mm_answer_keyallowed (ssh=0x3c32612f4000, sock=7, m=0x3c3261214d40)
>     at /usr/src/crypto/openssh/monitor.c:1205
> #8  0x000019c6b20f034d in monitor_read (ssh=ssh@entry=0x3c32612f4000, pmonitor=pmonitor@entry=0x3c32612c4cc0, 
>     ent=0x19c6b210a720 <mon_dispatch_proto20+208>, pent=pent@entry=0x19ced2ed0758)
>     at /usr/src/crypto/openssh/monitor.c:523
> #9  0x000019c6b20efdf2 in monitor_child_preauth (ssh=ssh@entry=0x3c32612f4000, pmonitor=0x3c32612c4cc0)
>     at /usr/src/crypto/openssh/monitor.c:298
> #10 0x000019c6b20cac27 in privsep_preauth (ssh=ssh@entry=0x3c32612f4000) at /usr/src/crypto/openssh/sshd-session.c:353
> #11 0x000019c6b20c9e3b in main (ac=2, av=<optimized out>) at /usr/src/crypto/openssh/sshd-session.c:1322
> (gdb) q
> 
> 
> Encountered on 2 machines:
> 
> Machine 1 "fbsd-next":
> 
> uname -v        -> FreeBSD 15.0-PRERELEASE #1 main-n279622-c992ac621327: Fri Aug 15 12:55:01 CEST 2025     root@fbsd-next:/usr/obj/usr/src/amd64.amd64/sys/GENERIC
> freebsd-version ->  15.0-PRERELEASE
> uname -UK       -> 1500060 1500060
> git branch -v   -> * main c992ac621327 ipheth(4): Add CDC-NCM support for RX
> git describe    -> vendor/NetBSD/bmake/20250804-302114-gc992ac621327
> 
> 
> (Machine 2 is currently rebuilding):
> 
> git branch -v -> * main 5205b32de3fb libc: Drop incorrect qsort optimization
> git describe  -> vendor/NetBSD/bmake/20250804-302115-g5205b32de3fb
> 
> Is anybody else experiencing same problem?

Yes, I can confirm the issue (arm64).
Downgrading to c75550e49997 resolved it for me.

--
Herbert