From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41930) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZHu0a-0002zL-05 for qemu-devel@nongnu.org; Wed, 22 Jul 2015 09:24:29 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZHu0Y-0000QG-UW for qemu-devel@nongnu.org; Wed, 22 Jul 2015 09:24:27 -0400 Date: Wed, 22 Jul 2015 15:24:16 +0200 From: Kevin Wolf Message-ID: <20150722132416.GA3349@noname.redhat.com> References: <1437570442-30203-1-git-send-email-rjones@redhat.com> <1437570442-30203-2-git-send-email-rjones@redhat.com> <20150722131050.GK12010@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150722131050.GK12010@redhat.com> Subject: Re: [Qemu-devel] [PATCH v2] block/ssh: Avoid segfault if inet_connect doesn't set errno. List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Daniel P. Berrange" Cc: jcody@redhat.com, "Richard W.M. Jones" , qemu-block@nongnu.org, qemu-devel@nongnu.org Am 22.07.2015 um 15:10 hat Daniel P. Berrange geschrieben: > On Wed, Jul 22, 2015 at 02:07:22PM +0100, Richard W.M. Jones wrote: > > On some (but not all) systems: > > > > $ qemu-img create -f qcow2 overlay -b ssh://xen/ > > Segmentation fault > > > > It turns out this happens when inet_connect returns -1 in the > > following code, but errno == 0. > > > > s->sock = inet_connect(s->hostport, errp); > > if (s->sock < 0) { > > ret = -errno; > > goto err; > > } > > > > In the test case above, no host called "xen" exists, so getaddrinfo fails. > > > > On Fedora 22, getaddrinfo happens to set errno = ENOENT (although it > > is *not* documented to do that), so it doesn't segfault. > > > > On RHEL 7, errno is not set by the failing getaddrinfo, so ret = > > -errno = 0, so the caller doesn't know there was an error and > > continues with a half-initialized BDRVSSHState struct, and everything > > goes south from there, eventually resulting in a segfault. > > > > Fix this by setting ret to -EINVAL. The real error is saved in the > > Error** errp struct, so it is printed correctly: > > > > $ ./qemu-img create -f qcow2 overlay -b ssh://xen/ > > qemu-img: overlay: address resolution failed for xen:22: No address associated with hostname > > > > Signed-off-by: Richard W.M. Jones > > Reported-by: Jun Li > > BZ: https://bugzilla.redhat.com/show_bug.cgi?id=1147343 > > --- > > block/ssh.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/block/ssh.c b/block/ssh.c > > index aebb18c..8d4dc2a 100644 > > --- a/block/ssh.c > > +++ b/block/ssh.c > > @@ -563,7 +563,7 @@ static int connect_to_ssh(BDRVSSHState *s, QDict *options, > > /* Open the socket and connect. */ > > s->sock = inet_connect(s->hostport, errp); > > if (s->sock < 0) { > > - ret = -errno; > > + ret = -EINVAL; > > goto err; > > There are a reasonable number of other uses of inet_connect() in QEMU, > so can't we fix inet_connect() itself to set EINVAL in the error case > instead of just fixing one caller. None of the other callers try to use errno, which isn't even documented as part of the inet_connect() interface. So I think setting errno inside inet_connect() would be wrong. If we were to change anything, we might consider returning -EINVAL instead of -1, though I'm not sure how useful that change would be. We would still have to fix this call in the ssh block driver. Kevin