[libvirt] [PATCH 2/8] qemuDomainBuildNamespace: Handle special file mount points

[John Ferlan]

On 06/22/2017 12:18 PM, Michal Privoznik wrote:
> https://bugzilla.redhat.com/show_bug.cgi?id=1459592
> 
> In 290a00e41d I've tried to fix the process of building a
> qemu namespace when dealing with file mount points. What I
> haven't realized then is that we might be dealing not with just
> regular files but also special files (like sockets). Indeed, try
> the following:
> 
> 1) socat unix-listen:/tmp/soket stdio
> 2) touch /dev/socket
> 3) mount --bind /tmp/socket /dev/socket
> 4) virsh start anyDomain
> 
> Problem with my previous approach is that I wasn't creating the
> temporary location (where mount points under /dev are moved) for
> anything but directories and regular files.
> 
> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
> ---
>  src/qemu/qemu_domain.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
> index 8e7404da6..212717c80 100644
> --- a/src/qemu/qemu_domain.c
> +++ b/src/qemu/qemu_domain.c
> @@ -8356,9 +8356,11 @@ qemuDomainBuildNamespace(virQEMUDriverConfigPtr cfg,
>              goto cleanup;
>          }
>  
> -        /* At this point, devMountsPath is either a regular file or a directory. */
> +        /* At this point, devMountsPath is either:
> +         * a file (regular or special), or
> +         * a directory. */
>          if ((S_ISDIR(sb.st_mode) && virFileMakePath(devMountsSavePath[i]) < 0) ||
> -            (S_ISREG(sb.st_mode) && virFileTouch(devMountsSavePath[i], sb.st_mode) < 0)) {
> +            (!S_ISDIR(sb.st_mode) && virFileTouch(devMountsSavePath[i], sb.st_mode) < 0)) {

It would seem to me that this would open Pandora's box to all different
types of things (BLK, CHR, FIFO, LNK, NAM, MPB, MPC, NWK) - some of
which it may not be so popular to perform a touch on.

I think you should keep it specific...  Perhaps use the list from
qemuDomainCreateDeviceRecursive:

   isReg = S_ISREG(sb.st_mode) || S_ISFIFO(sb.st_mode) ||
S_ISSOCK(sb.st_mode);

John

(FWIW: I used a cscope search on S_ISSOCK...)


>              virReportSystemError(errno,
>                                   _("Failed to create %s"),
>                                   devMountsSavePath[i]);
>