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Date: Thu, 17 Nov 2011 15:46:12 +0000
Message-ID: <CAJSP0QX7wK_sd1=yyiDt1uh0KhCSCUkQXvFaOWFmxQB2s3JyBA@mail.gmail.com>
From: Stefan Hajnoczi <stefanha@gmail.com>
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Subject: Re: [Qemu-devel] [PATCH V2 04/12] hw/9pfs: Open and create files
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To: "M. Mohan Kumar" <mohan@in.ibm.com>
Cc: qemu-devel@nongnu.org, aneesh.kumar@linux.vnet.ibm.com

On Tue, Nov 15, 2011 at 11:57 AM, M. Mohan Kumar <mohan@in.ibm.com> wrote:
> +static void send_fd(int sockfd, int fd)
> +{
> + =A0 =A0struct msghdr msg =3D { };
> + =A0 =A0struct iovec iov;
> + =A0 =A0struct cmsghdr *cmsg;
> + =A0 =A0int retval, data;
> + =A0 =A0union MsgControl msg_control;
> +
> + =A0 =A0iov.iov_base =3D &data;
> + =A0 =A0iov.iov_len =3D sizeof(data);
> +
> + =A0 =A0memset(&msg, 0, sizeof(msg));
> + =A0 =A0msg.msg_iov =3D &iov;
> + =A0 =A0msg.msg_iovlen =3D 1;
> + =A0 =A0/* No ancillary data on error */
> + =A0 =A0if (fd < 0) {
> + =A0 =A0 =A0 =A0/*
> + =A0 =A0 =A0 =A0 * fd is really negative errno if the request failed. Or=
 simply
> + =A0 =A0 =A0 =A0 * zero if the request is successful and it doesn't need=
 a file
> + =A0 =A0 =A0 =A0 * descriptor.
> + =A0 =A0 =A0 =A0 */

It cannot be zero because the if statement is fd < 0.  The comment is confu=
sing.

> +/*
> + * create a file and send fd on success
> + * return -errno on error
> + */
> +static int do_create(struct iovec *iovec)
> +{
> + =A0 =A0V9fsString path;
> + =A0 =A0int flags, fd, mode, uid, gid, cur_uid, cur_gid;
> + =A0 =A0proxy_unmarshal(iovec, 1, HDR_SZ, "sdddd",
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 &path, &flags, &mode, &uid, &gid);

Unmarshalling can fail if the iovec size does not match what the
format string describes.  We should fail here rather than continuing
on.  If execution continues some of the variables may be
uninitialized.

Stefan