Fix integer overflow OOB reads in Block::DecodeEntry and ReadBlock - #1353
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DecodeEntry: the bounds check (limit - p) < (non_shared + value_length) used uint32_t addition which wraps on overflow, allowing a crafted block entry to bypass the check and cause an out-of-bounds read in ParseNextKey. Fix by checking each field sequentially against the remaining space. ReadBlock: n + kBlockTrailerSize can overflow size_t when handle.size() is near SIZE_MAX, causing an undersized allocation followed by an OOB read at data[n]. Fix by rejecting unreasonable block sizes and checking for arithmetic overflow before allocation. Both bugs are reachable via crafted SST files and confirmed under AddressSanitizer.
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Discovered by Maliq Barnard. ASAN-confirmed integer overflow → heap-buffer-overflow in Block::DecodeEntry (uint32 wrap) and ReadBlock (size_t wrap) via crafted SST files. |
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Summary
Two integer overflow bugs in the SST table reader allow crafted SST files to trigger heap-buffer-overflow reads. Both confirmed under AddressSanitizer.
Bug 1: uint32 overflow in
DecodeEntry(table/block.cc:71)The bounds check
static_cast<uint32_t>(limit - p) < (*non_shared + *value_length)wraps whennon_shared + value_lengthexceeds 2^32. A crafted entry withnon_shared=50, value_length=0xFFFFFFD0wraps the sum to 2, bypasses the check, thenkey_.append(p, 50)reads 50 bytes from a buffer with only 5 remaining.Fix: Check each field sequentially against remaining space instead of summing.
Bug 2:
size_toverflow inReadBlock(table/format.cc:78)new char[n + kBlockTrailerSize]wraps whenhandle.size()is near SIZE_MAX, allocating a tiny buffer. Thendata[n]at line 102 reads at offset ~SIZE_MAX.Fix: Cap block size at 64MB and check for arithmetic overflow before allocation.
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