[libvirt] [PATCH] libxl: fix libvirtd segfault

[Dave Allan]

Functional ack; this patch fixes the crash on my system.

On Fri, Aug 09, 2013 at 05:58:45PM -0600, Jim Fehlig wrote:
> Commit d72ef888 introduced a bug in the libxl driver that will
> segfault libvirtd if libxl reports an error message, e.g. when
> attempting to initialize the driver on a non-Xen system.  I
> assumed it was valid to pass a NULL logger to libxl_ctx_alloc(),
> but that is not the case since any errors associated with the ctx
> that are emitted by libxl will dereference the logger and crash
> libvirtd.
> 
> Errors associated with the libxl driver-wide ctx could be useful
> for debugging anyway, so create a 'libxl-driver.log' to capture
> these errors.
> ---
>  src/libxl/libxl_conf.h   |  3 +++
>  src/libxl/libxl_driver.c | 30 ++++++++++++++++++++++++++++--
>  2 files changed, 31 insertions(+), 2 deletions(-)
> 
> diff --git a/src/libxl/libxl_conf.h b/src/libxl/libxl_conf.h
> index 78133b9..9d72b72 100644
> --- a/src/libxl/libxl_conf.h
> +++ b/src/libxl/libxl_conf.h
> @@ -57,6 +57,9 @@ struct _libxlDriverPrivate {
>      virDomainXMLOptionPtr xmlopt;
>      unsigned int version;
>  
> +    /* log stream for driver-wide libxl ctx */
> +    FILE *logger_file;
> +    xentoollog_logger *logger;
>      /* libxl ctx for driver wide ops; getVersion, getNodeInfo, ... */
>      libxl_ctx *ctx;
>  
> diff --git a/src/libxl/libxl_driver.c b/src/libxl/libxl_driver.c
> index cc9e772..9dc7261 100644
> --- a/src/libxl/libxl_driver.c
> +++ b/src/libxl/libxl_driver.c
> @@ -1180,6 +1180,9 @@ libxlStateCleanup(void)
>      virObjectUnref(libxl_driver->xmlopt);
>      virObjectUnref(libxl_driver->domains);
>      libxl_ctx_free(libxl_driver->ctx);
> +    xtl_logger_destroy(libxl_driver->logger);
> +    if (libxl_driver->logger_file)
> +        VIR_FORCE_FCLOSE(libxl_driver->logger_file);
>  
>      virObjectUnref(libxl_driver->reservedVNCPorts);
>  
> @@ -1229,6 +1232,7 @@ libxlStateInitialize(bool privileged,
>                       void *opaque ATTRIBUTE_UNUSED)
>  {
>      const libxl_version_info *ver_info;
> +    char *log_file = NULL;
>      virCommandPtr cmd;
>      int status, ret = 0;
>      unsigned int free_mem;
> @@ -1308,6 +1312,17 @@ libxlStateInitialize(bool privileged,
>          goto error;
>      }
>  
> +    if (virAsprintf(&log_file, "%s/libxl-driver.log", libxl_driver->logDir) < 0)
> +        goto error;
> +
> +    if ((libxl_driver->logger_file = fopen(log_file, "a")) == NULL)  {
> +        virReportSystemError(errno,
> +                             _("failed to create logfile %s"),
> +                             log_file);
> +        goto error;
> +    }
> +    VIR_FREE(log_file);
> +
>      /* read the host sysinfo */
>      if (privileged)
>          libxl_driver->hostsysinfo = virSysinfoRead();
> @@ -1316,8 +1331,18 @@ libxlStateInitialize(bool privileged,
>      if (!libxl_driver->domainEventState)
>          goto error;
>  
> -    if (libxl_ctx_alloc(&libxl_driver->ctx, LIBXL_VERSION, 0, NULL)) {
> -        VIR_INFO("cannot initialize libxenlight context, probably not running in a Xen Dom0, disabling driver");
> +    libxl_driver->logger =
> +            (xentoollog_logger *)xtl_createlogger_stdiostream(libxl_driver->logger_file, XTL_DEBUG, 0);
> +    if (!libxl_driver->logger) {
> +        VIR_INFO("cannot create logger for libxenlight, disabling driver");
> +        goto fail;
> +    }
> +
> +    if (libxl_ctx_alloc(&libxl_driver->ctx,
> +                       LIBXL_VERSION, 0,
> +                       libxl_driver->logger)) {
> +        VIR_INFO("cannot initialize libxenlight context, probably not running "
> +                 "in a Xen Dom0, disabling driver");
>          goto fail;
>      }
>  
> @@ -1383,6 +1408,7 @@ libxlStateInitialize(bool privileged,
>  error:
>      ret = -1;
>  fail:
> +    VIR_FREE(log_file);
>      if (libxl_driver)
>          libxlDriverUnlock(libxl_driver);
>      libxlStateCleanup();
> -- 
> 1.8.1.4
> 
> --
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