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Re: [PATCH v3 09/16] fuzz: add a crossover function to generic-fuzzer
From: |
Alexander Bulekov |
Subject: |
Re: [PATCH v3 09/16] fuzz: add a crossover function to generic-fuzzer |
Date: |
Thu, 15 Oct 2020 09:43:38 -0400 |
Thanks, I added some clarifications, but I added them to 02/16 (where I
first define and use SEPARATOR).
On 201001 1631, Darren Kenny wrote:
> As mentioned in an earlier patch, maybe the definition of SEPARATOR
> should be here as well as some of the comments you provided in the
> replies to it.
>
> Otherwise, this looks good,
>
> Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
>
> Thanks,
>
> Darren.
>
> On Sunday, 2020-09-20 at 22:24:59 -04, Alexander Bulekov wrote:
> > Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
> > ---
> > tests/qtest/fuzz/general_fuzz.c | 90 ++++++++++++++++++++++++++++++++-
> > 1 file changed, 89 insertions(+), 1 deletion(-)
> >
> > diff --git a/tests/qtest/fuzz/general_fuzz.c
> > b/tests/qtest/fuzz/general_fuzz.c
> > index 656ec7fd55..3833b505c8 100644
> > --- a/tests/qtest/fuzz/general_fuzz.c
> > +++ b/tests/qtest/fuzz/general_fuzz.c
> > @@ -741,6 +741,92 @@ static void general_pre_fuzz(QTestState *s)
> >
> > counter_shm_init();
> > }
> > +
> > +/*
> > + * When libfuzzer gives us two inputs to combine, return a new input with
> > the
> > + * following structure:
> > + *
> > + * Input 1 (data1)
> > + * SEPARATOR
> > + * Clear out the DMA Patterns
> > + * SEPARATOR
> > + * Disable the pci_read/write instructions
> > + * SEPARATOR
> > + * Input 2 (data2)
> > + *
> > + * The idea is to collate the core behaviors of the two inputs.
> > + * For example:
> > + * Input 1: maps a device's BARs, sets up three DMA patterns, and triggers
> > + * device functionality A
> > + * Input 2: maps a device's BARs, sets up one DMA pattern, and triggers
> > device
> > + * functionality B
> > + *
> > + * This function attempts to produce an input that:
> > + * Ouptut: maps a device's BARs, set up three DMA patterns, triggers
> > + * functionality A device, replaces the DMA patterns with a single
> > + * patten, and triggers device functionality B.
> > + */
> > +static size_t general_fuzz_crossover(const uint8_t *data1, size_t size1,
> > const
> > + uint8_t *data2, size_t size2, uint8_t
> > *out,
> > + size_t max_out_size, unsigned int
> > seed)
> > +{
> > + size_t copy_len = 0, size = 0;
> > +
> > + /* Check that we have enough space for data1 and at least part of
> > data2 */
> > + if (max_out_size <= size + strlen(SEPARATOR) * 3 + 2) {
> > + return 0;
> > + }
> > +
> > + /* Copy_Len in the first input */
> > + copy_len = size1;
> > + memcpy(out + size, data1, copy_len);
> > + size += copy_len;
> > + max_out_size -= copy_len;
> > +
> > + /* Append a separator */
> > + copy_len = strlen(SEPARATOR);
> > + memcpy(out + size, SEPARATOR, copy_len);
> > + size += copy_len;
> > + max_out_size -= copy_len;
> > +
> > + /* Clear out the DMA Patterns */
> > + copy_len = 1;
> > + if (copy_len) {
> > + out[size] = OP_CLEAR_DMA_PATTERNS;
> > + }
> > + size += copy_len;
> > + max_out_size -= copy_len;
> > +
> > + /* Append a separator */
> > + copy_len = strlen(SEPARATOR);
> > + memcpy(out + size, SEPARATOR, copy_len);
> > + size += copy_len;
> > + max_out_size -= copy_len;
> > +
> > + /* Disable PCI ops. Assume data1 took care of setting up PCI */
> > + copy_len = 1;
> > + if (copy_len) {
> > + out[size] = OP_DISABLE_PCI;
> > + }
> > + size += copy_len;
> > + max_out_size -= copy_len;
> > +
> > + /* Append a separator */
> > + copy_len = strlen(SEPARATOR);
> > + memcpy(out + size, SEPARATOR, copy_len);
> > + size += copy_len;
> > + max_out_size -= copy_len;
> > +
> > + /* Copy_Len over the second input */
> > + copy_len = MIN(size2, max_out_size);
> > + memcpy(out + size, data2, copy_len);
> > + size += copy_len;
> > + max_out_size -= copy_len;
> > +
> > + return size;
> > +}
> > +
> > +
> > static GString *general_fuzz_cmdline(FuzzTarget *t)
> > {
> > GString *cmd_line = g_string_new(TARGET_NAME);
> > @@ -760,7 +846,9 @@ static void register_general_fuzz_targets(void)
> > .description = "Fuzz based on any qemu command-line args. ",
> > .get_init_cmdline = general_fuzz_cmdline,
> > .pre_fuzz = general_pre_fuzz,
> > - .fuzz = general_fuzz});
> > + .fuzz = general_fuzz,
> > + .crossover = general_fuzz_crossover
> > + });
> > }
> >
> > fuzz_target_init(register_general_fuzz_targets);
> > --
> > 2.28.0