Re: Expected msgrcv(2) behaviour with msgsz > SSIZE_MAX ?

[christos%astron.com@localhost (Christos Zoulas)]

In article <20090102153241.GA102025%medusa.sis.pasteur.fr@localhost>,
Nicolas Joly  <njoly%pasteur.fr@localhost> wrote:
>
>Hi,
>
>While running LTP (Linux Testsuite Project) testcases under
>compat_linux on my -current NetBSD/amd64 workstation, i discovered
>that a testcase for msgrcv(2) syscall with msgsz < 0 was hanging
>instead of failing with EINVAL.
>
>Looking into this one, i noticed that the syscall man page state that
>a negative msgsz value make it fail with errno set to EINVAL, but the
>corresponding code does not seems to match.
>
>As size_t type is unsigned, this can never happen ... But, at the same
>time, the OpenGroup specification says that `msgsz > SSIZE_MAX' is
>implementation dependant (test i can easily convert to `(ssize_t)msgsz
>< 0', which was probably meant).
>
>I'm pretty sure that our implementation does handle this nicely. Can
>someone confirm that both man page and compat linux emulation needs to
>be fixed ?

The manual page needs to be fixed to remove the comment that < 0 == EINVAL,
and say that:

In this implementation if the value of msgsz exceeds SSIZE_MAX,
.Fn msgrcv 
will wait forever for a message to arrive.

or we should just check and return -1/E2BIG or EINVAL, which seems more
useful to me.

christos