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Fix a rare failure for imgdiff when random data equals gzip header

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In a rare case, a random chunk will pass both the gzip header check
and the inflation process; but fail the uncompressed length check in the
footer. This leads to a imgdiff failure. So, we should treat this chunk
as 'normal' instead of 'inflated' while generating the patch.

Bug: 63334984
Test: imgdiff generates patch successfully on previous failing images.
Change-Id: Ice84f22d3653bce9756bda91e70528c0d2f264a0
This commit is contained in:
Tianjie Xu
2017-07-05 12:04:07 -07:00
parent c8e338fa9c
commit 14ebc1e5ae
2 changed files with 47 additions and 11 deletions
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25
applypatch/imgdiff.cpp
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@@ -693,6 +693,20 @@ static bool ReadImage(const char* filename, std::vector<ImageChunk>* chunks,
continue;
}
// The footer contains the size of the uncompressed data. Double-check to make sure that it
// matches the size of the data we got when we actually did the decompression.
size_t footer_index = pos + raw_data_len + GZIP_FOOTER_LEN - 4;
if (sz - footer_index < 4) {
printf("Warning: invalid footer position; treating as a nomal chunk\n");
continue;
}
size_t footer_size = get_unaligned<uint32_t>(img->data() + footer_index);
if (footer_size != uncompressed_len) {
printf("Warning: footer size %zu != decompressed size %zu; treating as a nomal chunk\n",
footer_size, uncompressed_len);
continue;
}
ImageChunk body(CHUNK_DEFLATE, pos, img, raw_data_len);
uncompressed_data.resize(uncompressed_len);
body.SetUncompressedData(std::move(uncompressed_data));
@@ -704,17 +718,6 @@ static bool ReadImage(const char* filename, std::vector<ImageChunk>* chunks,
chunks->emplace_back(CHUNK_NORMAL, pos, img, GZIP_FOOTER_LEN);
pos += GZIP_FOOTER_LEN;
// The footer (that we just skipped over) contains the size of
// the uncompressed data. Double-check to make sure that it
// matches the size of the data we got when we actually did
// the decompression.
size_t footer_size = get_unaligned<uint32_t>(img->data() + pos - 4);
if (footer_size != body.DataLengthForPatch()) {
printf("Error: footer size %zu != decompressed size %zu\n", footer_size,
body.GetRawDataLength());
return false;
}
} else {
// Use a normal chunk to take all the contents until the next gzip chunk (or EOF); we expect
// the number of chunks to be small (5 for typical boot and recovery images).