Re: [PATCH 3/4] fuzz: setting bits in operand of out/write to zero

[Alexander Bulekov <alxndr@bu.edu>]

On 201220 0256, Qiuhao Li wrote:
> Simplifying the crash cases by opportunistically setting bits in
> operands of
> out/write to zero may help to debug, since usually bit one means turn on
> or
> trigger a function while zero is the default turn-off setting.
> 
> Tested Bug 1908062. Refined vs. Original result:
> 
> outl 0xcf8 0x8000081c            outl 0xcf8 0x8000081c
> outb 0xcfc 0xc3                  outb 0xcfc 0xc3
> outl 0xcf8 0x0               <-- outl 0xcf8 0x8000082f
> outl 0xcf8 0x80000804            outl 0xcf8 0x80000804
> outl 0xcfc 0x10000006        <-- outl 0xcfc 0x9b2765be
> write 0xc300001024 0x2 0x10  <-- write 0xc300001024 0x2 0x0055
> write 0xc300001028 0x1 0x5a      write 0xc300001028 0x1 0x5a
> write 0xc30000101c 0x1 0x01      write 0xc30000101c 0x1 0x01
> writel 0xc30000100c 0x2a6f6c63   writel 0xc30000100c 0x2a6f6c63
> write 0xc300001018 0x1 0x80  <-- write 0xc300001018 0x1 0xa4
> write 0x5c 0x1 0x10          <-- write 0x5c 0x1 0x19
> write 0xc300003002 0x1 0x0   <-- write 0xc300003002 0x1 0x8a
> 
> Signed-off-by: Qiuhao Li <Qiuhao.Li@outlook.com>

Looks good. One nit below.

Reviewed-by: Alexander Bulekov <alxndr@bu.edu>


> ---
>  scripts/oss-fuzz/minimize_qtest_trace.py | 42 +++++++++++++++++++++++-
>  1 file changed, 41 insertions(+), 1 deletion(-)
> 
> diff --git a/scripts/oss-fuzz/minimize_qtest_trace.py b/scripts/oss-fuzz/minimize_qtest_trace.py
> index 855c3bcb54..f3e88064c4 100755
> --- a/scripts/oss-fuzz/minimize_qtest_trace.py
> +++ b/scripts/oss-fuzz/minimize_qtest_trace.py
> @@ -172,7 +172,47 @@ def minimize_trace(inpath, outpath):
>                      newtrace[i] = prior
>                      del newtrace[i+1]
>          i += 1
> -    check_if_trace_crashes(newtrace, outpath)
> +
> +    assert(check_if_trace_crashes(newtrace, outpath))
> +
> +    TIMEOUT = (end-start)*2 # input is short now
> +
> +    # try setting bits in operands of out/write to zero
> +    i = 0
> +    while i < len(newtrace):
> +        if (not newtrace[i].startswith("write ") and not
> +           newtrace[i].startswith("out")):
> +           i += 1
> +           continue
> +        # write ADDR SIZE DATA
> +        # outx ADDR VALUE
> +        print("\nzero setting bits: {}".format(newtrace[i]))
> +
> +        prefix = " ".join(newtrace[i].split()[:-1])
> +        data = newtrace[i].split()[-1]
> +        data_bin = bin(int(data, 16))
> +        data_bin_list = list(data_bin)
> +
> +        for j in range(2, len(data_bin_list)):
> +            prior = newtrace[i]
> +            if (data_bin_list[j] == '1'):
> +                data_bin_list[j] = '0'
> +                data_try = hex(int("".join(data_bin_list), 2))
> +                # It seems qtest only accect hex with one byte zero padding
                                         ^^ "accepts padded hex-values."

> +                if len(data_try) % 2 == 1:
> +                    data_try = data_try[:2] + "0" + data_try[2:-1]
> +
> +                newtrace[i] = "{prefix} {data_try}\n".format(
> +                        prefix=prefix,
> +                        data_try=data_try)
> +
> +                if not check_if_trace_crashes(newtrace, outpath):
> +                    data_bin_list[j] = '1'
> +                    newtrace[i] = prior
> +
> +        i += 1
> +
> +    assert(check_if_trace_crashes(newtrace, outpath))
>  
>  
>  if __name__ == '__main__':
> -- 
> 2.25.1
>