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Message-ID: <20120626173205.GK544@brightrain.aerifal.cx>
Date: Tue, 26 Jun 2012 13:32:05 -0400
From: Rich Felker <dalias@...ifal.cx>
To: musl@...ts.openwall.com
Subject: Re: openssh and sendmsg() problem
On Wed, Jun 27, 2012 at 01:24:41AM +0800, orc wrote:
> On Tue, 26 Jun 2012 12:01:06 -0400
> Rich Felker <dalias@...ifal.cx> wrote:
>
> > On Tue, Jun 26, 2012 at 02:00:17PM +0200, Szabolcs Nagy wrote:
> > > * orc <orc@...server.ru> [2012-06-26 19:01:46 +0800]:
> > > > strace shows that sendmsg system call returns EINVAL:
> > > >
> > > > sendmsg(5, {msg_name(0)=NULL, msg_iov(1)=[{"\0", 1}],
> > > > msg_controllen=24, {cmsg_len=20, cmsg_level=SOL_SOCKET, cmsg_
> > > > type=SCM_RIGHTS, {4, 385875968}}, msg_flags=0}, 0) = -1 EINVAL
> > > > (Invalid argument)
> > > >
> > >
> > > src/network/sendmsg.c has an ifdef for long>int case
> > >
> > > i don't know what it's supposed to do
> >
> > It's there because the kernel expects certain fields to be long but
> > POSIX requires them to be int. Thus the syscall wrapper has to copy
> > the userspace struct (with int and padding) to a kernel-format struct
> > (with the padding filled with 0's so it's a valid long).
>
> And how to deal with this? Should it be openssh workaround or fix in
> musl itself?
There's nothing to be dealt with here; musl already works around the
kernel bug. Something is wrong, possibly in this code or elsewhere,
but I don't know what and I don't see anything obviously wrong with
the syscall. Can you compare the strace to what happens on glibc?
Rich
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