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-rw-r--r--softmmu/physmem.c10
-rw-r--r--tests/qtest/fuzz-test.c51
2 files changed, 61 insertions, 0 deletions
diff --git a/softmmu/physmem.c b/softmmu/physmem.c
index 3027747c03..2cd1de4a2c 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -3255,6 +3255,7 @@ int64_t address_space_cache_init(MemoryRegionCache *cache,
     AddressSpaceDispatch *d;
     hwaddr l;
     MemoryRegion *mr;
+    Int128 diff;
 
     assert(len > 0);
 
@@ -3263,6 +3264,15 @@ int64_t address_space_cache_init(MemoryRegionCache *cache,
     d = flatview_to_dispatch(cache->fv);
     cache->mrs = *address_space_translate_internal(d, addr, &cache->xlat, &l, true);
 
+    /*
+     * cache->xlat is now relative to cache->mrs.mr, not to the section itself.
+     * Take that into account to compute how many bytes are there between
+     * cache->xlat and the end of the section.
+     */
+    diff = int128_sub(cache->mrs.size,
+		      int128_make64(cache->xlat - cache->mrs.offset_within_region));
+    l = int128_get64(int128_min(diff, int128_make64(l)));
+
     mr = cache->mrs.mr;
     memory_region_ref(mr);
     if (memory_access_is_direct(mr, is_write)) {
diff --git a/tests/qtest/fuzz-test.c b/tests/qtest/fuzz-test.c
index 87b72307a5..cdb1100a0b 100644
--- a/tests/qtest/fuzz-test.c
+++ b/tests/qtest/fuzz-test.c
@@ -48,6 +48,55 @@ static void test_lp1878642_pci_bus_get_irq_level_assert(void)
     qtest_quit(s);
 }
 
+/*
+ * Here a MemoryRegionCache pointed to an MMIO region but had a
+ * larger size than the underlying region.
+ */
+static void test_mmio_oob_from_memory_region_cache(void)
+{
+    QTestState *s;
+
+    s = qtest_init("-M pc-q35-5.2 -display none -m 512M "
+		   "-device virtio-scsi,num_queues=8,addr=03.0 ");
+
+    qtest_outl(s, 0xcf8, 0x80001811);
+    qtest_outb(s, 0xcfc, 0x6e);
+    qtest_outl(s, 0xcf8, 0x80001824);
+    qtest_outl(s, 0xcf8, 0x80001813);
+    qtest_outl(s, 0xcfc, 0xa080000);
+    qtest_outl(s, 0xcf8, 0x80001802);
+    qtest_outl(s, 0xcfc, 0x5a175a63);
+    qtest_outb(s, 0x6e08, 0x9e);
+    qtest_writeb(s, 0x9f003, 0xff);
+    qtest_writeb(s, 0x9f004, 0x01);
+    qtest_writeb(s, 0x9e012, 0x0e);
+    qtest_writeb(s, 0x9e01b, 0x0e);
+    qtest_writeb(s, 0x9f006, 0x01);
+    qtest_writeb(s, 0x9f008, 0x01);
+    qtest_writeb(s, 0x9f00a, 0x01);
+    qtest_writeb(s, 0x9f00c, 0x01);
+    qtest_writeb(s, 0x9f00e, 0x01);
+    qtest_writeb(s, 0x9f010, 0x01);
+    qtest_writeb(s, 0x9f012, 0x01);
+    qtest_writeb(s, 0x9f014, 0x01);
+    qtest_writeb(s, 0x9f016, 0x01);
+    qtest_writeb(s, 0x9f018, 0x01);
+    qtest_writeb(s, 0x9f01a, 0x01);
+    qtest_writeb(s, 0x9f01c, 0x01);
+    qtest_writeb(s, 0x9f01e, 0x01);
+    qtest_writeb(s, 0x9f020, 0x01);
+    qtest_writeb(s, 0x9f022, 0x01);
+    qtest_writeb(s, 0x9f024, 0x01);
+    qtest_writeb(s, 0x9f026, 0x01);
+    qtest_writeb(s, 0x9f028, 0x01);
+    qtest_writeb(s, 0x9f02a, 0x01);
+    qtest_writeb(s, 0x9f02c, 0x01);
+    qtest_writeb(s, 0x9f02e, 0x01);
+    qtest_writeb(s, 0x9f030, 0x01);
+    qtest_outb(s, 0x6e10, 0x00);
+    qtest_quit(s);
+}
+
 int main(int argc, char **argv)
 {
     const char *arch = qtest_get_arch();
@@ -59,6 +108,8 @@ int main(int argc, char **argv)
                        test_lp1878263_megasas_zero_iov_cnt);
         qtest_add_func("fuzz/test_lp1878642_pci_bus_get_irq_level_assert",
                        test_lp1878642_pci_bus_get_irq_level_assert);
+        qtest_add_func("fuzz/test_mmio_oob_from_memory_region_cache",
+                       test_mmio_oob_from_memory_region_cache);
     }
 
     return g_test_run();