Core dump issue when using Cygwin SSH alongside OpenSSH for Windows

[Indranil Chakraborty]

git version 2.45.2.windows.1

Windows environment screenshot below

Windows bundled SSH version is OpenSSH_for_Windows_8.6p1, LibreSSL 3.4.3

---------

Repro steps:

1. Ensure Windows 11 system is as above and the OpenSSH bundled client is installed.

2. Install git version 2.45.2.windows.1 on Windows 11 computer running the above environment. Configure such as to use Cygwin OpenSSH.

3. Run a simple SSH (e.g. ssh -T g...@github.com) command or git pull. Core dump error is thrown.

E.g.

$ git pull
      0 [main] ssh 2036 cygwin_exception::open_stackdumpfile: Dumping stack trace to ssh.exe.stackdump

Error log.

$ cat ssh.exe.stackdump
Exception: STATUS_ACCESS_VIOLATION at rip=00010046E620
rax=00007FF8F3D9E000 rbx=0000000A0004F350 rcx=0000000000000000
rdx=0000000000000133 rsi=0000000A00056550 rdi=00000007FFFFAA98
r8 =00007FF8F3D958B0 r9 =0000000000000001 r10=0000000800000000
r11=000000010045993A r12=0000000000000000 r13=0000000000000000
r14=00007FF8F3D86DC0 r15=00007FF8F3D80000
rbp=00000007FFFFAAA0 rsp=00000007FFFFA860
program=C:\Program Files\Git\usr\bin\ssh.exe, pid 2036, thread main
cs=0033 ds=002B es=002B fs=0053 gs=002B ss=002B
Stack trace:
Frame         Function      Args
0007FFFFAAA0  00010046E620 (000A00043D70, 000000001000, 000000000000, 000100000001) ssh.exe+0x6E620
000100498F75  000100492603 (000A000028F8, 0002102258A0, 5C5C5C5C5C5C5C5C, 615C705C6C5C6C5C) ssh.exe+0x92603
0007FFFFCD30  000210047F01 (000000000000, 000000000000, 000000000000, 000000000000) msys-2.0.dll+0x7F01
000000000000  000210045AC3 (000000000000, 000000000000, 000000000000, 000000000000) msys-2.0.dll+0x5AC3
0007FFFFFFF0  000210045B74 (000000000000, 000000000000, 000000000000, 000000000000) msys-2.0.dll+0x5B74
End of stack trace
Loaded modules:
000100400000 ssh.exe
7FF90C2D0000 ntdll.dll
7FF90B460000 KERNEL32.DLL
7FF909A40000 KERNELBASE.dll
0004356F0000 msys-crypto-3.dll
0004F53C0000 msys-gssapi-3.dll
000522FE0000 msys-z.dll
000210040000 msys-2.0.dll
0005E8160000 msys-gcc_s-seh-1.dll
0004901D0000 msys-asn1-8.dll
000419420000 msys-com_err-1.dll
0005FE970000 msys-heimntlm-0.dll
0005889A0000 msys-heimbase-1.dll
0004A4450000 msys-hcrypto-4.dll
0004E6EC0000 msys-krb5-26.dll
0005FE2A0000 msys-roken-18.dll
000497010000 msys-wind-0.dll
00043DBF0000 msys-crypt-0.dll
00047F610000 msys-hx509-5.dll
0005798A0000 msys-sqlite3-0.dll
7FF90AEB0000 advapi32.dll
7FF90B5C0000 msvcrt.dll
7FF90B170000 sechost.dll
7FF909FE0000 bcrypt.dll
7FF90BA50000 RPCRT4.dll
7FF908E70000 CRYPTBASE.DLL
7FF909670000 bcryptPrimitives.dll
7FF90AE30000 ws2_32.dll
7FF908B90000 mswsock.dll
7FF8E1C40000 napinsp.dll
7FF909920000 ucrtbase.dll
7FF8E1C20000 pnrpnsp.dll
7FF907DB0000 DNSAPI.dll
7FF907D80000 IPHLPAPI.DLL
7FF90B220000 NSI.dll
7FF8DE610000 winrnr.dll
7FF8DE550000 wshbth.dll
7FF8DE520000 nlansp_c.dll
7FF909DF0000 msvcp_win.dll
7FF903C60000 dhcpcsvc6.DLL
7FF903AD0000 dhcpcsvc.DLL
7FF906A20000 WINNSI.DLL
7FF8FBA70000 rasadhlp.dll
7FF9010C0000 fwpuclnt.dll
7FF8F3D80000 libykcs11.dll
7FF8F5320000 VCRUNTIME140.dll
7FF8ED330000 libykpiv.dll
7FF8B6D50000 libcrypto-1_1-x64.dll
7FF9097B0000 CRYPT32.dll
7FF90B6E0000 USER32.dll
7FF909FB0000 win32u.dll
7FF8F3820000 WinSCard.dll
7FF90A990000 GDI32.dll
7FF909E90000 gdi32full.dll
7FF90A010000 IMM32.DLL

Issue persists through reboots / uninstall + reinstall / etc.

Issue also persists if I remove Windows native SSH and use only Cygwin SSH (which I found surprising).

Issue resolved if I uninstall + reinstall and choose native SSH.

--------

Cheers,

Thanks for all the hard work the community does!

--Neil.

[Johannes Schindelin]

Hi Neil,

while it works most of the time to call Cygwin executables from MSYS
executables (such as the Bash distributed with Git for Windows), it
sometimes fails in these hard-to-fix ways.

It is best to avoid such situations.

In your instance, it may be better to not only use Cygwin's SSH but also
Cygwin's `git`.

Ciao,
Johannes

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