blob: d04cf8a8bec905078ad970e05b69607f901bfcf7 (
plain) (
blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
|
[CRASH] OpenGL acceleration except gtk: bad interaction between NVIDIA usermode opengl libraries and QEMU seccomp -sandbox on,spawn=deny, crashes immediately on startup with Bad system call
Description of problem:
When running any of the above command lines, QEMU crashes with Bad system call (core dumped). Not exclusive to spice; it seems this is caused by QEMU forking during OpenGL initialization after seccomp takes effect.
Steps to reproduce:
1. Run the above commandline
2. Notice a Bad system call (core dumped)
Additional information:
This crash only happens if spawn=deny is set, resourcecontrol/obsolete/elevateprivileges don't cause crashes.
The crash happens around the same time as an audit event is generated in dmesg: `audit: type=1326 audit(1705775880.776:14): auid=MYUSERID uid=MYUID gid=MYGID ses=REDACTED pid=REDACTED comm="qemu-system-x86" exe="/usr/bin/qemu-system-x86_64" sig=31 arch=c000003e syscall=56 compat=0 ip=REDACTED code=REDACTED`
`ausyscall c000003e 56` tells me it's `clone` which (iirc) is the syscall used by glibc to implement fork() (I might be wrong about glibc part)
Suggested solution: move seccomp activation until just before guest code starts executing? make frontends (ie -display gtk/sdl/whatever, including -spice) initialize before seccomp?
Workaround: `chmod -x /bin/nvidia-modprobe` if not using the NVIDIA gpu or use this wrapper script (untested, not enterprise-ready, I am not responsible if unexpected things happen):
- rename /bin/qemu-system-x86_64 to qemu-system-x86_64.real
- put this in /bin/qemu-system-x86_64 and chmod +x it
```sh
#!/usr/bin/env sh
chmod -x /bin/nvidia-modprobe
qemu-system-x86_64.real $@ & disown
sleep 10 # excessive but maybe safer?
chmod +x /bin/nvidia-modprobe
```
Also, you can use -display gtk,gl=on instead, or (unknown security implications) remove spawn=deny from -sandbox args
original bug report was https://gitlab.com/libvirt/libvirt/-/issues/585 but I realized this was more of a qemu issue than a libvirt one
|