kernel: reject empty argv (argv[0] == nil) in sysexec()

when executing a script, we did advance argp0 unconditionally
to replace argv[0] with the script name. this fails when
argv[] is empty, then we'd advance argp0 past the nil terminator.

the alternative would be to *not* advance if *argp0 == nil, but that
would require another validaddr() check for a case that is unlikely
to have been anticipated in most programs being invoked as
libc's ARGBEGIN macro assumes argv[0] being non-nil as it also
unconditionally advances the argv pointer.

to keep us sane, we now reject an empty argv[]. on entry, we
verify that argv[] is valid for at least two elements:
- the program name argv[0], has to be non-nil
- the first potential nil terminator in argv[1]

when argv[0] == nil, we throw Ebadarg "bad arg in system call"

0 files changed, 0 insertions, 0 deletions