Sporadic segmentation faults when running nixos-rebuild on NixOS

[alexeymuranov]

From time to time a get a segmentation fault when i do nixos-rebuild boot --upgrade.

It used to happen on the older of two machines on which i am trying NixOS, but it has just happened on the newer one too:

# nixos-rebuild boot --upgrade
/run/current-system/sw/bin/nixos-rebuild: line 208:  2595 Segmentation fault      nix-channel --update nixos

Trying nixos-rebuild second time normally works. I do not know how to reliably reproduce this either.

System info:

# nix-shell -p nix-info --run "nix-info -m"
 - system: `"x86_64-linux"`
 - host os: `Linux 4.19.55-hardened, NixOS, 19.03.172968.3ddd23719bb (Koi)`
 - multi-user?: `no`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.2.2`
 - channels(alexey): `"nixos-17.03-17.03.1949.78e9665b48f, nixos-17.09-17.09.3238.e984f9e48e1"`
 - channels(root): `"nixos-19.03.172968.3ddd23719bb"`
 - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixos`

[Ekleog]

As you appear to be using -hardened, does anything interesting appear in dmesg when this happens? (it should be possible to find it in journalctl too, if you have rebooted since the last time this happened)

[alexeymuranov]

I haven't rebooted yet, here is what i have in dmesg:

[  500.653973] fuse init (API version 7.27)
[  506.734127] rfkill: input handler disabled
[  831.481141] show_signal_msg: 2 callbacks suppressed
[  831.481153] nix-channel[2600]: segfault at 8 ip 00007f2263fbd330 sp 00007f2249106190 error 4 in libc-2.27.so[7f2263f71000+13d000]
[  831.481186] Code: 85 db 0f 84 22 01 00 00 8b 01 49 89 fc 49 89 f2 49 89 c9 25 00 80 00 00 75 59 4c 8b 81 88 00 00 00 64 48 8b 2c 25 10 00 00 00 <49> 3b 68 08 74 3e be 01 00 00 00 83 3d 76 74 14 00 00 74 09 f0 41

I should note that the older machine uses "plain" Linux 4.19, and there this or similar segfault was observed multiple times. On the newer machine that has Linux 4.19 hardened, this is the first one.

[sorpaas]

I'm having a similar error when trying to run a game in steam-fhs:

[22864.736592] ThreeKingdoms[13273]: segfault at 0 ip 00007fcb3d80b4b1 sp 00007fcad7fec108 error 4 in libc-2.27.so[7fcb3d6db000+13d000]
[22864.736597] Code: 84 00 00 00 00 00 0f 1f 00 31 c0 c5 f8 77 c3 66 2e 0f 1f 84 00 00 00 00 00 89 f9 48 89 fa c5 f9 ef c0 83 e1 3f 83 f9 20 77 1f <c5> fd 74 0f c5 fd d7 c1 85 c0 0f 85 df 00 00 00 48 83 c7 20 83 e1

[domenkozar]

Make sure to get a core dump and run bt.

[zimbatm]

@alexeymuranov's segfault is probably related to #2733 . nixos-rebuild <action> --upgrade calls nix-channel --update under the hood. You could test that by running nix-channel --upgrade and then nixos-rebuild boot and see which one segfaults.

@sorpaas's segfault happens inside of a game. It's best to report this in the nixpkgs repo.