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Re: [libvirt] [PATCH] Honor blacklist for modprobe command



On Tue, Jan 28, 2014 at 07:00:16PM -0500, John Ferlan wrote:
> https://bugzilla.redhat.com/show_bug.cgi?id=1045124
> 
> When loading modules, libvirt does not honor the modprobe blacklist.
> By adding a "-b" to the modprobe command libvirt will fail to load a
> module if it's on the blacklist
> 
> Check if the failure to load a driver was due to it being on the blacklist
> using the output of a "modprobe -c" searching for "blacklist <driver_Name>"
> where driver_Name is possibly a modified string of the input driver changing
> all '-' into '_' since that's what modprobe does.
> 
> Signed-off-by: John Ferlan <jferlan redhat com>
> ---
>  src/util/virpci.c | 48 ++++++++++++++++++++++++++++++++++++++++++------
>  1 file changed, 42 insertions(+), 6 deletions(-)
> 
> diff --git a/src/util/virpci.c b/src/util/virpci.c
> index e2d222e..18b85f2 100644
> --- a/src/util/virpci.c
> +++ b/src/util/virpci.c
> @@ -979,6 +979,10 @@ virPCIProbeStubDriver(const char *driver)
>  {
>      char *drvpath = NULL;
>      bool probed = false;
> +    size_t i;
> +    char *drvblklst = NULL;
> +    char *outbuf = NULL;
> +    virCommandPtr cmd = NULL;
>  
>  recheck:
>      if (virPCIDriverDir(&drvpath, driver) == 0 && virFileExists(drvpath)) {
> @@ -990,18 +994,49 @@ recheck:
>      VIR_FREE(drvpath);
>  
>      if (!probed) {
> -        const char *const probecmd[] = { MODPROBE, driver, NULL };
> +        cmd = virCommandNewArgList(MODPROBE, "-b", driver, NULL);
>          probed = true;
> -        if (virRun(probecmd, NULL) < 0) {
> +        if (virCommandRun(cmd, NULL) < 0) {
>              char ebuf[1024];
>              VIR_WARN("failed to load driver %s: %s", driver,
>                       virStrerror(errno, ebuf, sizeof(ebuf)));
> -            return -1;
> +            goto cleanup;
>          }
> +        virCommandFree(cmd);
> +        cmd = NULL;
>  
>          goto recheck;
>      }
>  
> +    /* All error path code - purpose is to determine whether the failure
> +     * occurs because device is on blacklist in order to add an error
> +     * message to help detect why load failed
> +     */
> +    if (virAsprintfQuiet(&drvblklst, "blacklist %s", driver) < 0)
> +        goto cleanup;
> +
> +    /* Although driver may have dash, 'modprobe -c' adjusts to use underscore */
> +    for (i = 0; i < drvblklst[i]; i++)
> +        if (drvblklst[i] == '-')
> +            drvblklst[i] = '_';
> +
> +    cmd = virCommandNewArgList(MODPROBE, "-c", NULL);
> +    virCommandSetOutputBuffer(cmd, &outbuf);
> +    if (virCommandRun(cmd, NULL) < 0)
> +        goto cleanup;
> +
> +    /* Find driver on blacklist? */
> +    if (strstr(outbuf, drvblklst)) {
> +        virReportError(VIR_ERR_INTERNAL_ERROR,
> +                       _("Failed to load PCI stub module %s: "
> +                         "administratively prohibited"),
> +                       driver);
> +    }
> +
> +cleanup:
> +    virCommandFree(cmd);
> +    VIR_FREE(drvblklst);
> +    VIR_FREE(outbuf);
>      return -1;
>  }

This is getting complex enough that I think we ought introduce
a src/util/virkmod.{c,h} and have some helper APIs in there
for loading and unload modules. eg virKModLoad, virKModUnload
etc

Regards,
Daniel
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