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Re: [Qemu-devel] [PATCH] block/ssh: Avoid segfault if inet_connect doesn
From: |
Richard W.M. Jones |
Subject: |
Re: [Qemu-devel] [PATCH] block/ssh: Avoid segfault if inet_connect doesn't set errno. |
Date: |
Wed, 22 Jul 2015 14:03:12 +0100 |
User-agent: |
Mutt/1.5.20 (2009-12-10) |
On Wed, Jul 22, 2015 at 01:07:53PM +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 NULL in the
> following code, but errno is not set (0).
Bleah .. not NULL, -1. I'm going to send an updated v2
patch which will just fix the message.
Rich.
> s->sock = inet_connect(s->hostport, errp);
> if (s->sock < 0) {
> ret = -errno;
> goto err;
> }
>
> In the case above, 'xen' doesn't exist 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 == 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.
>
> Fix this by setting errno 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
>
> BZ: https://bugzilla.redhat.com/show_bug.cgi?id=1147343
> Signed-off-by: Richard W.M. Jones <address@hidden>
> ---
> 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;
> }
>
> --
> 2.4.3
>
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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