tree 7506b286fe92d45bd893589f19ebf2ecf0971ebd
parent ee7f21ea4a84871d0e6d085d93b49a876656d0a8
author Jorge Gorbe Moya <jgorbe@google.com> 1586295882 -0700
committer Copybara-Service <copybara-worker@google.com> 1598638595 -0700

[libunwind] Fix UB in EHHeaderParser::findFDE

When the EHHeaderInfo object filled by decodeEHHdr has fde_count == 0,
findFDE does the following:

- sets low = 0 and len = hdrInfo.fde_count as a preparation to start a
  binary search
- because len is 0, the binary search loop is skipped
- the code still tries to find a table entry at
  hdrInfo.table + low * tableEntrySize, and decode it.

This is wrong when fde_count is 0, and trying to decode a table entry
that isn't there will lead to reading garbage offsets and can cause
segfaults.

Differential Revision: https://reviews.llvm.org/D77679

GitOrigin-RevId: 82576d6fecfec71725eb900111c000d772002449