Merge "imgdiff: skip spurious gzip headers in image files"

applypatch/imgdiff.cpp

@@ -407,6 +407,7 @@ unsigned char* ReadImage(const char* filename,
   while (pos < sz) {
     unsigned char* p = img+pos;
 
+    bool processed_deflate = false;
     if (sz - pos >= 4 &&
         p[0] == 0x1f && p[1] == 0x8b &&
         p[2] == 0x08 &&    // deflate compression
@@ -460,18 +461,24 @@ unsigned char* ReadImage(const char* filename,
         strm.next_out = curr->data + curr->len;
         ret = inflate(&strm, Z_NO_FLUSH);
         if (ret < 0) {
-            printf("Error: inflate failed [%s] at file offset [%zu]\n"
+          if (!processed_deflate) {
-                    "imgdiff only supports gzip kernel compression,"
+            // This is the first chunk, assume that it's just a spurious
-                    " did you try CONFIG_KERNEL_LZO?\n",
+            // gzip header instead of a real one.
-                    strm.msg, chunk_offset);
+            break;
-            free(img);
+          }
-            return NULL;
+          printf("Error: inflate failed [%s] at file offset [%zu]\n"
+                 "imgdiff only supports gzip kernel compression,"
+                 " did you try CONFIG_KERNEL_LZO?\n",
+                 strm.msg, chunk_offset);
+          free(img);
+          return NULL;
         }
         curr->len = allocated - strm.avail_out;
         if (strm.avail_out == 0) {
           allocated *= 2;
           curr->data = reinterpret_cast<unsigned char*>(realloc(curr->data, allocated));
         }
+        processed_deflate = true;
       } while (ret != Z_STREAM_END);
 
       curr->deflate_len = sz - strm.avail_in - pos;