Re: [PATCH v2] run QEMU as non-root

[Ian Campbell <ian.campbell@citrix.com>]

On Fri, 2015-05-15 at 15:28 +0100, Ian Jackson wrote:
> Stefano Stabellini writes ("[PATCH v2] run QEMU as non-root"):
> > +2) a user named "xen-qemudepriv-base", adding domid to its uid
> > +If xen-qemudepriv-base has uid 6000, and the domid is 25, libxl will try
> > +to use uid 6025. To use this mechanism, you might want to create a large
> > +number of users at installation time. For example:
> 
> You should document explicitly, and not just in the example, that this
> will require the reservation of 65536 uids from the uid of
> xen-qemudepriv-base to that uid+65535.
> 
> > +        buf_size = sysconf(_SC_GETPW_R_SIZE_MAX);
> > +        if (buf_size < 0) {
> > +            LOGE(ERROR, "sysconf(_SC_GETPW_R_SIZE_MAX) returned error %ld", buf_size);
> > +            goto end_search;
> > +        }
> > +        buf = libxl__malloc(gc, buf_size);
> 
> This is not the correct use of getpwnam_r.  getpwnam_r is allowed to
> fail with ERANGE even if the buffer you provide is as big as the
> sysconf requested.
> 
> But: is qemu at this point actually multithreaded ?  If not then
> plain getpwnam is probably better...

This code is in libxl not qemu...

Ian.