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, 5 deletions

diff --git a/include/exec/memory.h b/include/exec/memory.h
index c6ce74fb79..ecba90bfd8 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -45,13 +45,11 @@ DECLARE_OBJ_CHECKERS(IOMMUMemoryRegion, IOMMUMemoryRegionClass,
 #ifdef CONFIG_FUZZ
 void fuzz_dma_read_cb(size_t addr,
                       size_t len,
-                      MemoryRegion *mr,
-                      bool is_write);
+                      MemoryRegion *mr);
 #else
 static inline void fuzz_dma_read_cb(size_t addr,
                                     size_t len,
-                                    MemoryRegion *mr,
-                                    bool is_write)
+                                    MemoryRegion *mr)
 {
     /* Do Nothing */
 }
@@ -2506,7 +2504,7 @@ address_space_read_cached(MemoryRegionCache *cache, hwaddr addr,
                           void *buf, hwaddr len)
 {
     assert(addr < cache->len && len <= cache->len - addr);
-    fuzz_dma_read_cb(cache->xlat + addr, len, cache->mrs.mr, false);
+    fuzz_dma_read_cb(cache->xlat + addr, len, cache->mrs.mr);
     if (likely(cache->ptr)) {
         memcpy(buf, cache->ptr + addr, len);
         return MEMTX_OK;