[libvirt] [PATCH] Change label of fusefs mounted at /proc/meminfo in lxc containers

[Daniel P. Berrange]

On Wed, May 15, 2013 at 09:46:29AM -0400, dwalsh at redhat.com wrote:
> From: Dan Walsh <dwalsh at redhat.com>
> 
> We do not want to allow contained applications to be able to read fusefs_t.
> So we want /proc/meminfo label to match the system default proc_t.
> ---
>  src/lxc/lxc_container.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/src/lxc/lxc_container.c b/src/lxc/lxc_container.c
> index ac0f69c..bba2e3a 100644
> --- a/src/lxc/lxc_container.c
> +++ b/src/lxc/lxc_container.c
> @@ -52,6 +52,10 @@
>  # include <blkid/blkid.h>
>  #endif
>  
> +#if WITH_SELINUX
> +# include <selinux/selinux.h>
> +#endif
> +
>  #include "virerror.h"
>  #include "virlog.h"
>  #include "lxc_container.h"
> @@ -763,6 +767,26 @@ static int lxcContainerMountProcFuse(virDomainDefPtr def,
>                             def->name)) < 0)
>          return ret;
>  
> +#if WITH_SELINUX
> +    if (is_selinux_enabled() > 0) {
> +        security_context_t scon;
> +        ret = getfilecon("/proc/meminfo", &scon);
> +        if (ret) {

This error handling is broken. The man page says

   'On success, a positive number is returned indicating the  size  of  the
    extended  attribute value. On failure, -1 is returned and errno is  set
    appropriately.'

so you must use   'if (ret < 0) {' for detecting errors.


> +            virReportSystemError(errno,
> +                                 _("Failed to get security context of %s for /proc/meminfo mount point"),
> +                                 meminfo_path);
> +            return ret;

Return -1;

> +        }
> +        ret = setfilecon(meminfo_path, scon);
> +        freecon(scon);
> +        if (ret) {

And again here.

> +            virReportSystemError(errno,
> +                                 _("Failed to set security context of %s for /proc/meminfo mount point"),
> +                                 meminfo_path);
> +            return ret;

Return -1;

> +        }
> +    }
> +#endif
>      if ((ret = mount(meminfo_path, "/proc/meminfo",
>                       NULL, MS_BIND, NULL)) < 0) {
>          virReportSystemError(errno,

Daniel
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