We received a bug report that the SSE-4.2-based strstr in glibc 2.17 was
misbehaving and returned NULL for certain inputs, even though the search
pattern is clearly present in the subject string.  I'm attaching a test
case.  You can run it as "./tst-strstr 3" to directly go to one failing
case.

I'm not sure how to debug this further, except by running the program
under GDB, single-step through it, dump registers, and compare the
results with a bare-metal implement after each instruction executed.

Downstream bug: https://bugzilla.redhat.com/show_bug.cgi?id=1270703
There is also an attachment with a pre-compiled binary.

Thanks,
Florian