vm: fix illegal memory access not being detected #83
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Summary ======= Fix VM memory access checks not rejecting memory access when the accessed memory region crosses the `uint64` upper limit, allowing for read/write access to outside the guest memory. Details ======= The test in `checkmem` did not account for unsigned integer wrap around. If `x` is greater than or equal to the start of the virtual memory and `x + len` wraps around, then no error was reported if the wrapped-around value was less than the virtual memory's upper limit. Unsigned integer wrap around is now explicitly tested for, leading to `checkmem` returning an error if detected.
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Summary
Fix VM memory access checks not rejecting memory access when the
accessed memory region crosses the
uint64upper limit, allowing forread/write access to outside the guest memory.
Details
The test in
checkmemdid not account for unsigned integer wraparound. If
xis greater than or equal to the start of the virtualmemory and
x + lenwraps around, then no error was reported if thewrapped-around value was less than the virtual memory's upper limit.
Unsigned integer wrap around is now explicitly tested for, leading to
checkmemreturning an error if detected.Notes For Reviewers