fork server handshake failed

[abhi spark]

i crosscompiled a c program to arm using arm-linux-gnueabi-gcc , then build the afl-qemu setting CPU_TARGET=arm ./bashscript . when i run the command afl-fuzz -i in/ -o out/ -Q --/path /to/fuzz/app @@ i get the fork server handshake failed , detailing memory insufficient . even i gave -m 6000 its the same replicating .

can some one say did i do anything wrong while executing?

thanks in advance

[Michal Zalewski]

> can some one say did i do anything wrong while executing?

Try running the program under afl-showmap, like so:

afl-showmap -o- -Q /path/to/target/binary [...params...]

It should allow you to see any error messages from QEMU or the target
program itself. Likely a cross-compilation or target arch issue, but
hard to tell.

/mz

[abhi spark]

i have ran afl-showmap and got output as no instrument detected.

[Michal Zalewski]

Well, the QEMU error message complains about not having enough memory.
Looks like it's trying to allocate a ton, so maybe just try '-m none'
to the afl-showmap command line (and if that works, also use it with
afl-fuzz)?

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[abhi spark]

Thanks , it worked  and found few crashes. but after some time it pops out error stating unable to communicate with fork server (00M?)  location run_target , i attached the screen shot.

[Michal Zalewski]

> Thanks , it worked and found few crashes. but after some time it pops out
> error stating unable to communicate with fork server (00M?) location
> run_target , i attached the screen shot.

You likely run out of memory when the program tries to allocate too
much of it due to some sort of a coding error (a consequence of
lifting the memory limit with -m none).

You could try to fine-tune the -m value so that the program runs but
can't crash other programs. There may be some other workarounds, but
they would be application-specific.

/mz

[abhi spark]

Thanks , yup now everything is working fine  setting AFL_NO_FORKSRV=1 solved my issue . thanks a lot lcamtuf :)

[Gen Zhang]

How to set  AFL_NO_FORKSRV=1?
Any specific steps?
Thanks

在 2017年1月24日星期二 UTC+8下午3:31:06，abhi spark写道：