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Avoid overflow when looking up address u64::MAX - #374
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yuxi-liu-wired wants to merge 1 commit into
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`ResUnits::find` computed `probe + 1`, which overflows for `probe == u64::MAX`. With overflow checks (debug builds) this panics in `Context::find_location` and `Context::find_frames`; in release builds it wraps to 0, which happens to find no units. Ranges are half-open, so no unit can contain `u64::MAX`; use `saturating_add` so the lookup returns no location and no frames. u64::MAX occurs in practice as a tombstone address in DWARF for discarded functions (e.g. lld fills relocations to dead code with -1), and lookups for such addresses come from untrusted backtraces and symbolization requests. Found by fuzzing addr2line with object's tombstone test files.
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ResUnits::findcomputedprobe + 1, which overflows forprobe == u64::MAX:find_locationandfind_framespanic in debug builds (release builds wrap to 0 and happen to find nothing).Ranges are half-open, so no unit can contain
u64::MAX;saturating_addkeeps the lookup returning nothing. u64::MAX shows up in practice as the tombstone address for discarded functions, and lookups come from arbitrary backtrace addresses.The new
max_addresstest fails on master. Found by fuzzing addr2line with object's tombstone test files.