[Bug 2505515] nss_sss: getpwnam results in a -1 fd being passed to fstat

https://bugzilla.redhat.com/show_bug.cgi?id=2505515

Noah Arcouette  changed:

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--- Comment #4 from Noah Arcouette  ---
Hello, no this does not cause any security issues, but it certainly shouldn't
be expected behaviour. I encountered this while using valgrind and originally
thought something terrible had occurred because my program raised a system call
fault within valgrind because -1 was being passed to fstat. I never used fstat
in the program and barely allocated any data. But, the issue was being raised
and data was left allocated. The data is fine, though annoying because I prefer
my apps freeing everything and I can't free data I didn't allocate, but that's
all normal behaviour as it wasn't leaked data just unfreed data.

What isn't normal behaviour is passing -1 to a system call. Why exactly are you
doing it this way? Why are you checking if a value is -1 by passing it to the
kernel and letting it yell at you?

In my opinion, passing -1 as an fd to the kernel should never be expect. It
causes debuggers -- specifically valgrind -- to raise one of its deepest
faults; no stack trace could be built, it was just a ghost error in my program
that made no sense to be there.

If this truly is expected behaviour, and you really do want the kernel to check
an integer for you, then you should at least create a valgrind suppression file
so people don't freak out when their program's passing -1 to a system call.

Thank you for your time,
  Noah