fuzzing: negation can result in overflow inside TextView::svtoi

[shukitchan]

Fuzzing finds out a potential problem in TextView.

The line in question is https://github.com/apache/trafficserver/blob/master/lib/swoc/src/TextView.cc#L64

zret = -zret

So LONG_MIN is -9223372036854775808 and LONG_MAX is 9223372036854775807
If zret is LONG_MIN, then -zret will result in overflow and it can result in an undefined behavior depending on the system.

The fuzzing finding for this problem is here - https://oss-fuzz.com/testcase-detail/5196561539530752
You can check out the details of this particular finding from ubsan here (under Unary Negation section) - https://wiki.sei.cmu.edu/confluence/display/c/INT32-C.+Ensure+that+operations+on+signed+integers+do+not+result+in+overflow

[shukitchan]

@SolidWallOfCode , can you give some advice here?

[SolidWallOfCode]

Fixed in this commit. There is other IP and Errata related work ongoing, when these are done there will be a new release for ATS (libswoc 1.5.9).

[shukitchan]

Problem is still there. I will take a look and attempt a fix next week