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Commit 671249a3 authored by Bowgo Tsai's avatar Bowgo Tsai
Browse files

fastboot: fix --disable-verifiation error message 

There is an unclear error message if we run
`fastboot --disable-verification flash boot boot.img` on a
AVB-disabled device without a /vbmeta partition.

Error message:
  terminating with uncaught exception of type std::out_of_range: basic_string
  Aborted

This is because the buf->fd of the loaded boot.img is not reset,
before returning from function copy_boot_avb_footer().

Also reset some changes in copy_boot_avb_footer() from commit
If83f785e235569ee8ef0de2b37f11dbd2a9a71f4, to prevent the
unnecessary read of the boot vbmeta if no need to copy the
boot image avb footer.

Bug: 191903922
Test: `fastboot --disable-verification flash boot boot.img` on a device
      without /vbmeta and without setting BOARD_AVB_ENABLE to true.
Change-Id: If84f08f1b2e12c4c6ded5cafda2bd1d30e75c662
parent 6e3f64e7

fastboot/fastboot.cpp

+21 −10
Original line number Diff line number Diff line
@@ -941,7 +941,8 @@ static void rewrite_vbmeta_buffer(struct fastboot_buffer* buf, bool vbmeta_in_bo 
        // Tries to locate top-level vbmeta from boot.img footer.

        uint64_t footer_offset = buf->sz - AVB_FOOTER_SIZE;

        if (0 != data.compare(footer_offset, AVB_FOOTER_MAGIC_LEN, AVB_FOOTER_MAGIC)) {

            die("Failed to find AVB_FOOTER at offset: %" PRId64, footer_offset);

            die("Failed to find AVB_FOOTER at offset: %" PRId64 ", is BOARD_AVB_ENABLE true?",

                footer_offset);

        }

        const AvbFooter* footer = reinterpret_cast<const AvbFooter*>(data.c_str() + footer_offset);

        vbmeta_offset = be64toh(footer->vbmeta_offset);
@@ -1021,6 +1022,24 @@ static void copy_boot_avb_footer(const std::string& partition, struct fastboot_b 
        return;

    }



    // If overflows and negative, it should be < buf->sz.

    int64_t partition_size = static_cast<int64_t>(get_partition_size(partition));



    if (partition_size == buf->sz) {

        return;

    }

    // Some device bootloaders might not implement `fastboot getvar partition-size:boot[_a|_b]`.

    // In this case, partition_size will be zero.

    if (partition_size < buf->sz) {

        fprintf(stderr,

                "Warning: skip copying boot image avb footer"

                " (boot partition size: %" PRId64 ", boot image size: %" PRId64 ").\n",

                partition_size, buf->sz);

        return;

    }



    // IMPORTANT: after the following read, we need to reset buf->fd before return (if not die).

    // Because buf->fd will still be used afterwards.

    std::string data;

    if (!android::base::ReadFdToString(buf->fd, &data)) {

        die("Failed reading from boot");
@@ -1028,17 +1047,9 @@ static void copy_boot_avb_footer(const std::string& partition, struct fastboot_b 


    uint64_t footer_offset = buf->sz - AVB_FOOTER_SIZE;

    if (0 != data.compare(footer_offset, AVB_FOOTER_MAGIC_LEN, AVB_FOOTER_MAGIC)) {

        lseek(buf->fd.get(), 0, SEEK_SET);  // IMPORTANT: resets buf->fd before return.

        return;

    }

    // If overflows and negative, it should be < buf->sz.

    int64_t partition_size = static_cast<int64_t>(get_partition_size(partition));



    if (partition_size == buf->sz) {

        return;

    }

    if (partition_size < buf->sz) {

        die("boot partition is smaller than boot image");

    }



    unique_fd fd(make_temporary_fd("boot rewriting"));

    if (!android::base::WriteStringToFd(data, fd)) {