fuzz: ignore address_space_map is_write flag

We passed an is_write flag to the fuzz_dma_read_cb function to
differentiate between the mapped DMA regions that need to be populated
with fuzzed data, and those that don't. We simply passed through the
address_space_map is_write parameter. The goal was to cut down on
unnecessarily populating mapped DMA regions, when they are not read
from.

Unfortunately, nothing precludes code from reading from regions mapped
with is_write=true. For example, see:
https://lists.gnu.org/archive/html/qemu-devel/2021-01/msg04729.html

This patch removes the is_write parameter to fuzz_dma_read_cb. As a
result, we will fill all mapped DMA regions with fuzzed data, ignoring
the specified transfer direction.

Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Message-Id: <20210120060255.558535-1-alxndr@bu.edu>

1 files changed, 3 insertions, 6 deletions

diff --git a/tests/qtest/fuzz/generic_fuzz.c b/tests/qtest/fuzz/generic_fuzz.c
index be76d47d2d..deb74f15be 100644
--- a/tests/qtest/fuzz/generic_fuzz.c
+++ b/tests/qtest/fuzz/generic_fuzz.c
@@ -175,7 +175,7 @@ static int memory_access_size(MemoryRegion *mr, unsigned l, hwaddr addr)
  * generic_fuzz(), avoiding potential race-conditions, which we don't have
  * a good way for reproducing right now.
  */
-void fuzz_dma_read_cb(size_t addr, size_t len, MemoryRegion *mr, bool is_write)
+void fuzz_dma_read_cb(size_t addr, size_t len, MemoryRegion *mr)
 {
     /* Are we in the generic-fuzzer or are we using another fuzz-target? */
     if (!qts_global) {
@@ -187,14 +187,11 @@ void fuzz_dma_read_cb(size_t addr, size_t len, MemoryRegion *mr, bool is_write)
      * - We have no DMA patterns defined
      * - The length of the DMA read request is zero
      * - The DMA read is hitting an MR other than the machine's main RAM
-     * - The DMA request is not a read (what happens for a address_space_map
-     *   with is_write=True? Can the device use the same pointer to do reads?)
      * - The DMA request hits past the bounds of our RAM
      */
     if (dma_patterns->len == 0
         || len == 0
         || mr != current_machine->ram
-        || is_write
         || addr > current_machine->ram_size) {
         return;
     }
@@ -213,12 +210,12 @@ void fuzz_dma_read_cb(size_t addr, size_t len, MemoryRegion *mr, bool is_write)
             double_fetch = true;
             if (addr < region.addr
                 && avoid_double_fetches) {
-                fuzz_dma_read_cb(addr, region.addr - addr, mr, is_write);
+                fuzz_dma_read_cb(addr, region.addr - addr, mr);
             }
             if (addr + len > region.addr + region.size
                 && avoid_double_fetches) {
                 fuzz_dma_read_cb(region.addr + region.size,
-                        addr + len - (region.addr + region.size), mr, is_write);
+                        addr + len - (region.addr + region.size), mr);
             }
             return;
         }