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Check overflow for memory read #121

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Check overflow for memory read #121

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6 changes: 6 additions & 0 deletions rvgo/fast/memory.go
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Original file line number Diff line number Diff line change
Expand Up @@ -283,6 +283,12 @@ func (r *memReader) Read(dest []byte) (n int, err error) {
return 0, io.EOF
}

if r.addr > 1<<64-1-r.count {
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Can r.count exceed 63 causing underflow? Maybe it makes sense to do the following?

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if r.addr > 1<<64-1-r.count {
if r.count < 64 && r.addr > 1<<64-1-r.count {

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This is done to check if the r.addr + r.count does not exceed uint64 max (1<<64-1). I think bit shift has higher operator precedence than subtraction, so underflow won't happen.

// If adding r.count to r.addr would exceed the maximum uint64 value,
// we consider that an overflow condition and stop.
return 0, io.EOF
}

// Keep iterating over memory until we have all our data.
// It may wrap around the address range, and may not be aligned
endAddr := r.addr + r.count
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