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executing_syzkaller_programs.md

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Executing syzkaller programs

This page describes how to execute existing syzkaller programs for the purpose of bug reproduction. This way you can replay a single program or a whole execution log with several programs.

  1. Setup Go toolchain (if you don't yet have it, you need version 1.13 or higher): Download latest Go distribution from (https://golang.org/dl/). Unpack it to $HOME/goroot.
$ export GOROOT=$HOME/goroot
$ export GOPATH=$HOME/gopath
  1. Download syzkaller sources:
$ go get -u -d github.com/google/syzkaller/prog
  1. Build necessary syzkaller binaries:
$ cd $GOPATH/src/github.com/google/syzkaller
$ make
  1. Copy binaries and the program to test machine (substitue target linux_amd64 as necessary):
$ scp -P 10022 -i stretch.img.key bin/linux_amd64/syz-execprog bin/linux_amd64/syz-executor program root@localhost:
  1. Run the program on the test machine:
$ ./syz-execprog -repeat=0 -procs=8 program

Several useful syz-execprog flags:

  -collide
    	collide syscalls to provoke data races (default true)
  -procs int
    	number of parallel processes to execute programs (default 1)
  -repeat int
    	repeat execution that many times (0 for infinite loop) (default 1)
  -sandbox string
    	sandbox for fuzzing (none/setuid/namespace) (default "setuid")
  -threaded
    	use threaded mode in executor (default true)

If you pass -threaded=0 -collide=0, programs will be executed as a simple single-threaded sequence of syscalls. -threaded=1 forces execution of each syscall in a separate thread, so that execution can proceed over blocking syscalls. -collide=1 forces second round of execution of syscalls when pairs of syscalls are executed concurrently.

If you are replaying a reproducer program that contains a header along the following lines:

#{Threaded:true Collide:true Repeat:true Procs:8 Sandbox:namespace
  Fault:false FaultCall:-1 FaultNth:0 EnableTun:true UseTmpDir:true
  HandleSegv:true WaitRepeat:true Debug:false Repro:false}

then you need to adjust syz-execprog flags based on the values in the header. Namely, Threaded/Collide/Procs/Sandbox directly relate to -threaded/-collide/-procs/-sandbox flags. If Repeat is set to true, add -repeat=0 flag to syz-execprog.