Troubleshooting

Here are some things to check if there are problems running syzkaller.

• Use the -debug command line option to make syzkaller print all possible debug output, from both the syz-manager top-level program and the syz-fuzzer instances. With this option syzkaller will only run one VM instance.

• Use the -vv N command line option to increase the amount of logging output, from both the syz-manager top-level program and the syz-fuzzer instances (which go to the output files in the crashes subdirectory of the working directory). Higher values of N give more output.

• If logging indicates problems with the executor program (e.g. executor failure), try manually running a short sequence of system calls:

  • Copy syz-executor and syz-execprog into a running VM.
  • In the VM run ./syz-execprog -executor ./syz-executor -debug sampleprog where sampleprog is a simple system call script (e.g. just containing getpid()).
  • For example, if this reports that clone has failed, this probably indicates that the test kernel does not include support for all of the required namespaces. In this case, running the syz-execprog test with the -sandbox=setuid option fixes the problem, so the main configuration needs to be updated to set sandbox to setuid.

• If syzkaller prinths the failed to copy binary error shortly after VM has booted:

  • If you’re using Buildroot images and the error output contains the subsystem request failed on channel 0 line, this can be due to the OpenSSH 9.0 changes that force the use of the SFTP protocol. Upgrade your Buildroot image to the latest version and make sure SFTP is enabled there.

Also see this for Linux kernel specific troubleshooting advice.

If none of the above helps, file a bug on the bug tracker or ask us directly on the syzkaller@googlegroups.com mailing list. Please include syzkaller commit id that you use and syz-manager output with -debug flag enabled if applicable.