Truncate vbmeta size to partition size am: da0c7cffd4 am: 0e68760ac3

Original change: https://android-review.googlesource.com/c/platform/external/avb/+/2400885

Change-Id: Iddc6a67da80d31d81ff8029b069b9e62663486d1
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>

1 files changed, 22 insertions, 18 deletions

diff --git a/libavb/avb_slot_verify.c b/libavb/avb_slot_verify.c
index 3a066f5..a548c80 100644
--- a/libavb/avb_slot_verify.c
+++ b/libavb/avb_slot_verify.c
@@ -558,22 +558,6 @@ out:
   return ret;
 }
 
-static AvbIOResult read_one_byte_from_partition(AvbOps* ops,
-                                                const char* partition_name) {
-  /* test_buf is a one-byte buffer used to check the existence of the
-   * current partition before allocating the big chunk of memory on heap
-   * for vbmeta later.
-   */
-  uint8_t test_buf[TEST_BUFFER_SIZE];
-  size_t test_num_read;
-  return ops->read_from_partition(ops,
-                                  partition_name,
-                                  0 /* offset */,
-                                  TEST_BUFFER_SIZE,
-                                  test_buf,
-                                  &test_num_read);
-}
-
 static AvbSlotVerifyResult load_and_verify_vbmeta(
     AvbOps* ops,
     const char* const* requested_partitions,
@@ -691,14 +675,34 @@ static AvbSlotVerifyResult load_and_verify_vbmeta(
         vbmeta_size = footer.vbmeta_size;
       }
     }
+  } else {
+    uint64_t partition_size = 0;
+    io_ret =
+        ops->get_size_of_partition(ops, full_partition_name, &partition_size);
+    if (io_ret == AVB_IO_RESULT_OK) {
+      if (partition_size < vbmeta_size && partition_size > 0) {
+        avb_debugv(full_partition_name,
+                   ": Using partition size as vbmeta size\n",
+                   NULL);
+        vbmeta_size = partition_size;
+      }
+    } else {
+      avb_debugv(full_partition_name, ": Failed to get partition size\n", NULL);
+      // libavb might fall back to other partitions if current vbmeta partition
+      // isn't found. So AVB_IO_RESULT_ERROR_NO_SUCH_PARTITION is recoverable,
+      // but other errors are not.
+      if (io_ret != AVB_IO_RESULT_ERROR_NO_SUCH_PARTITION) {
+        ret = AVB_SLOT_VERIFY_RESULT_ERROR_IO;
+        goto out;
+      }
+    }
   }
 
-  /* Read one byte from the partition to check the existence of the
+  /* Use result from previous I/O operation to check the existence of the
    * partition before allocating the big chunk of memory on heap
    * for vbmeta later. `io_ret` will be used later to decide whether
    * to fallback on the `boot` partition.
    */
-  io_ret = read_one_byte_from_partition(ops, full_partition_name);
   if (io_ret != AVB_IO_RESULT_ERROR_NO_SUCH_PARTITION) {
     vbmeta_buf = avb_malloc(vbmeta_size);
     if (vbmeta_buf == NULL) {