CDRIVER-5506 error if mongoc_gridfs_file_readv reads an incomplete chunk
#1565
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Fixes a possible hang when `mongoc_gridfs_file_readv` is called with a corrupt interior chunk sized smaller than `chunk_size`. Implementation assumes chunks (excluding the last chunk) are of size `chunk_size` for calcluating offsets.
kevinAlbs
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Mar 29, 2024
…chunk (#1565) * include more info in error message * add regression test for reading incomplete chunk * CDRIVER-5506 error if reading an incomplete chunk Fixes a possible hang when `mongoc_gridfs_file_readv` is called with a corrupt interior chunk sized smaller than `chunk_size`. Implementation assumes chunks (excluding the last chunk) are of size `chunk_size` for calcluating offsets.
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Summary
Address a hang observed in
mongoc_gridfs_file_readvwhen reading a corrupt incomplete chunk. If an incomplete chunk is detected, an error is now returned.Background & Motivation
Though the
mongoc_gridfs_tAPI notably does not conform to the GridFS spec, the GridFS spec requires returning an error for an unexpected length:The cause of the hang is an assumption that chunks (excluding the last) contain data of length chunk size.
_mongoc_gridfs_file_refresh_pagecalculates the chunk to read from the position of the last read byte:If an incomplete chunk is read,
file->posmay be smaller than assumed, resulting in repeated setting offile->nto an already-read chunk.