diff --git a/block/dmg.c b/block/dmg.c
index c571ac91213820ec9de4c18ad31b228faf00b1ae..04bae729a4765033cc6ac21c92beb51f2d5e7c12 100644
--- a/block/dmg.c
+++ b/block/dmg.c
@@ -285,60 +285,38 @@ fail:
     return ret;
 }
 
-static int dmg_open(BlockDriverState *bs, QDict *options, int flags,
-                    Error **errp)
+static int dmg_read_resource_fork(BlockDriverState *bs, DmgHeaderState *ds,
+                                  uint64_t info_begin, uint64_t info_length)
 {
-    BDRVDMGState *s = bs->opaque;
-    DmgHeaderState ds;
-    uint64_t info_begin, info_end;
-    uint32_t count, rsrc_data_offset;
-    int64_t offset;
     int ret;
+    uint32_t count, rsrc_data_offset;
+    uint64_t info_end;
+    uint64_t offset;
 
-    bs->read_only = 1;
-    s->n_chunks = 0;
-    s->offsets = s->lengths = s->sectors = s->sectorcounts = NULL;
-    /* used by dmg_read_mish_block to keep track of the current I/O position */
-    ds.last_in_offset = 0;
-    ds.last_out_offset = 0;
-    ds.max_compressed_size = 1;
-    ds.max_sectors_per_chunk = 1;
-
-    /* locate the UDIF trailer */
-    offset = dmg_find_koly_offset(bs->file, errp);
-    if (offset < 0) {
-        ret = offset;
-        goto fail;
-    }
-
-    ret = read_uint64(bs, offset + 0x28, &info_begin);
-    if (ret < 0) {
-        goto fail;
-    } else if (info_begin == 0) {
-        ret = -EINVAL;
-        goto fail;
-    }
-
+    /* read offset from begin of resource fork (info_begin) to resource data */
     ret = read_uint32(bs, info_begin, &rsrc_data_offset);
     if (ret < 0) {
         goto fail;
-    } else if (rsrc_data_offset != 0x100) {
+    } else if (rsrc_data_offset > info_length) {
         ret = -EINVAL;
         goto fail;
     }
 
-    ret = read_uint32(bs, info_begin + 4, &count);
+    /* read length of resource data */
+    ret = read_uint32(bs, info_begin + 8, &count);
     if (ret < 0) {
         goto fail;
-    } else if (count == 0) {
+    } else if (count == 0 || rsrc_data_offset + count > info_length) {
         ret = -EINVAL;
         goto fail;
     }
-    /* end of resource data, ignoring the following resource map */
-    info_end = info_begin + count;
 
     /* begin of resource data (consisting of one or more resources) */
-    offset = info_begin + 0x100;
+    offset = info_begin + rsrc_data_offset;
+
+    /* end of resource data (there is possibly a following resource map
+     * which will be ignored). */
+    info_end = offset + count;
 
     /* read offsets (mish blocks) from one or more resources in resource data */
     while (offset < info_end) {
@@ -352,13 +330,63 @@ static int dmg_open(BlockDriverState *bs, QDict *options, int flags,
         }
         offset += 4;
 
-        ret = dmg_read_mish_block(bs, &ds, offset, count);
+        ret = dmg_read_mish_block(bs, ds, offset, count);
         if (ret < 0) {
             goto fail;
         }
         /* advance offset by size of resource */
         offset += count;
     }
+    return 0;
+
+fail:
+    return ret;
+}
+
+static int dmg_open(BlockDriverState *bs, QDict *options, int flags,
+                    Error **errp)
+{
+    BDRVDMGState *s = bs->opaque;
+    DmgHeaderState ds;
+    uint64_t rsrc_fork_offset, rsrc_fork_length;
+    int64_t offset;
+    int ret;
+
+    bs->read_only = 1;
+    s->n_chunks = 0;
+    s->offsets = s->lengths = s->sectors = s->sectorcounts = NULL;
+    /* used by dmg_read_mish_block to keep track of the current I/O position */
+    ds.last_in_offset = 0;
+    ds.last_out_offset = 0;
+    ds.max_compressed_size = 1;
+    ds.max_sectors_per_chunk = 1;
+
+    /* locate the UDIF trailer */
+    offset = dmg_find_koly_offset(bs->file, errp);
+    if (offset < 0) {
+        ret = offset;
+        goto fail;
+    }
+
+    /* offset of resource fork (RsrcForkOffset) */
+    ret = read_uint64(bs, offset + 0x28, &rsrc_fork_offset);
+    if (ret < 0) {
+        goto fail;
+    }
+    ret = read_uint64(bs, offset + 0x30, &rsrc_fork_length);
+    if (ret < 0) {
+        goto fail;
+    }
+    if (rsrc_fork_length != 0) {
+        ret = dmg_read_resource_fork(bs, &ds,
+                                     rsrc_fork_offset, rsrc_fork_length);
+        if (ret < 0) {
+            goto fail;
+        }
+    } else {
+        ret = -EINVAL;
+        goto fail;
+    }
 
     /* initialize zlib engine */
     s->compressed_chunk = qemu_try_blockalign(bs->file,