Fuzzer-found issue #57237 (buffer boundary condition)

[cowtowncoder]

Looks like there is a buffer read boundary condition that OSSFuzz has found wrt TOMLParser:

https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=57237

I added a (failing) unit test to reproduce

 com.fasterxml.jackson.dataformat.toml.failing.FuzzTomlRead57237Test

[cowtowncoder]

cc @yawkat

[yawkat]

I added a fix

@lsf37 FYI, I think this is an upstream issue in jflex too (same as #403). Unfortunately we use a modified skeleton for our own buffer management, so I can't be 100% sure this appears in the default jflex skeleton. But these two bugs happened in the parts that should not be modified. I'm having a hard time working with the jflex build (bazel :/ ), so haven't managed to contribute upstream yet. You may want to take a look at these issues to see if they can be fixed in jflex.

[lsf37]

Interesting. I'll have a look at that, I thought this should be fixed by now, but I might be wrong.

[cowtowncoder]

Thank you @yawkat , @lsf37 .