On Mon, Dec 22, 2014 at 11:48:29AM +0800, Jason Wang wrote:
>
> On 12/19/2014 09:25 PM, Amos Kong wrote:
> > Passing some invalid fds in QEMU commandline, the fds don't exist.
> > QEMU will get error "TUNGETIFF ioctl() failed: Bad file descriptor",
> > and coredump in setting queues.
> >
> > This patch checked return value of first operate to fd, QEMU will
> > report error and exit without coredump. It's effected for both netdev
> > fds and vhost_net fds.
> >
> > Signed-off-by: Amos Kong <ak...@redhat.com>
> > ---
> > net/tap.c | 16 +++++++++++++---
> > 1 file changed, 13 insertions(+), 3 deletions(-)
> >
> > diff --git a/net/tap.c b/net/tap.c
> > index bde6b58..039280a 100644
> > --- a/net/tap.c
> > +++ b/net/tap.c
> > @@ -688,7 +688,7 @@ int net_init_tap(const NetClientOptions *opts, const
> > char *name,
> > NetClientState *peer)
> > {
> > const NetdevTapOptions *tap;
> > - int fd, vnet_hdr = 0, i = 0, queues;
> > + int fd, vnet_hdr = 0, i = 0, queues, ret;
> > /* for the no-fd, no-helper case */
> > const char *script = NULL; /* suppress wrong "uninit'd use" gcc
> > warning */
> > const char *downscript = NULL;
> > @@ -722,7 +722,12 @@ int net_init_tap(const NetClientOptions *opts, const
> > char *name,
> > return -1;
> > }
> >
> > - fcntl(fd, F_SETFL, O_NONBLOCK);
> > + ret = fcntl(fd, F_SETFL, O_NONBLOCK);
> > + if (ret < 0) {
> > + error_report("Fail to set file status to nonblock, "
> > + "%s", strerror(-ret));
> > + return -1;
> > + }
>
> This may not work. There may be still some kinds of fd can pass this but
> still fail at TUNGETIFF or other tun ioctls.
Early catching the error is better. This only help to check if the fd
exists.
> Probably you need to fail during TUNGETIFF, which can make sure it was
> not a tap fd.
Currently if ioctl fails, we treat the IFF_VNET_HDR flag isn't set.
We can return -1 in this case, and checking return value of
tap_probe_vnet_hdr(),
and fail qemu.
qemu/net/tap-linux.c:
int tap_probe_vnet_hdr(int fd)
{
struct ifreq ifr;
if (ioctl(fd, TUNGETIFF, &ifr) != 0) {
error_report("TUNGETIFF ioctl() failed: %s", strerror(errno));
return 0; <============
}
return ifr.ifr_flags & IFF_VNET_HDR;
}
I think we can fix tap_probe_vnet_hdr() and add checking return value of
fcntl().
--
Amos.
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