[PATCH 0/3] out-of-bounds access from corrupted .idx files

[Jeff King <peff@peff.net>]

This series teaches Git to detect a few problems with corrupted .idx
files, and adds tests for some more cases.  There's conceptually some
overlap with t5300, but I don't think it was covering any of these cases
explicitly.

There are two real bugs that could cause segfaults or bus errors via
bogus reads (but never writes). On top of that, these are all problems
in .idx files, which are usually generated locally. So I don't think
there's anything particularly security interesting here. You'd need a
situation where you convince somebody to read your .idx files (so maybe
a multi-user server), and then I don't see how you'd turn it into remote
code execution.

I think with these patches, fuzzing .idx files should never result in
any memory problems (though of course git will die()).  Famous last
words, of course. I stopped short of poking at other file formats, which
might have similar issues. Obvious candidates are .bitmap files, and the
on-disk $GIT_DIR/index.

  [1/3]: t5313: test bounds-checks of corrupted/malicious pack/idx files
  [2/3]: nth_packed_object_offset: bounds-check extended offset
  [3/3]: use_pack: handle signed off_t overflow

-Peff