Re: [Qemu-devel] [PATCH v8 6/9] module: add configurable module whitelist

["Daniel P. Berrange" <berrange@redhat.com>]

On Fri, Sep 13, 2013 at 04:38:51PM +0800, Fam Zheng wrote:
> Accept configure option "--enable-modules=L", to restrict qemu to only
> load whitelisted modules.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>  configure             | 12 +++++++++++-
>  rules.mak             |  7 ++++++-
>  scripts/create_config |  7 +++++++
>  util/module.c         | 16 ++++++++++++++++
>  4 files changed, 40 insertions(+), 2 deletions(-)
> 
> diff --git a/configure b/configure
> index 3043059..01e3665 100755
> --- a/configure
> +++ b/configure
> @@ -652,7 +652,9 @@ for opt do
>    ;;
>    --disable-debug-info)
>    ;;
> -  --enable-modules) modules="yes"
> +  --enable-modules|--enable-modules=*)
> +      modules="yes"
> +      module_list=`echo "$optarg" | sed -e 's/,/ /g'`
>    ;;
>    --cpu=*)
>    ;;
> @@ -1060,6 +1062,8 @@ echo "  --sysconfdir=PATH        install config in PATH$confsuffix"
>  echo "  --localstatedir=PATH     install local state in PATH (set at runtime on win32)"
>  echo "  --with-confsuffix=SUFFIX suffix for QEMU data inside datadir and sysconfdir [$confsuffix]"
>  echo "  --enable-modules         enable modules support"
> +echo "  --enable-modules=L       enable modules and provide a whitelist"
> +echo "                           Available modules: curl iscsi gluster ssh rbd"
>  echo "  --enable-debug-tcg       enable TCG debugging"
>  echo "  --disable-debug-tcg      disable TCG debugging (default)"
>  echo "  --enable-debug-info       enable debugging information (default)"
> @@ -3590,6 +3594,9 @@ if test "$slirp" = "yes" ; then
>      echo "smbd              $smbd"
>  fi
>  echo "module support    $modules"
> +if test -n "$module_list"; then
> +    echo "module whitelist  $module_list"
> +fi
>  echo "host CPU          $cpu"
>  echo "host big endian   $bigendian"
>  echo "target list       $target_list"
> @@ -3711,6 +3718,9 @@ echo "ARCH=$ARCH" >> $config_host_mak
>  echo "CONFIG_FINGERPRINT=$(date +%s$$$RANDOM)" >> $config_host_mak
>  if test "$modules" = "yes"; then
>    echo "CONFIG_MODULES=y" >> $config_host_mak
> +  if test -n "$module_list"; then
> +      echo "CONFIG_MODULE_WHITELIST=$module_list" >> $config_host_mak
> +  fi
>  fi
>  case "$cpu" in
>    arm|i386|x86_64|x32|ppc|aarch64)
> diff --git a/rules.mak b/rules.mak
> index 0670366..e5529da 100644
> --- a/rules.mak
> +++ b/rules.mak
> @@ -165,13 +165,18 @@ $(if $(nested-dirs),
>    $(call unnest-vars-1))
>  endef
>  
> +is-whitelisted = $(if $(CONFIG_MODULE_WHITELIST),$(strip \
> +    $(filter $(CONFIG_MODULE_WHITELIST),$(basename $(notdir $1)))),\
> +	yes)
>  define add-modules
>  $(foreach o,$(filter %.o,$($1)),
>  	$(eval $(patsubst %.o,%.mo,$o): $o) \
>  	$(eval $(patsubst %.o,%.mo,$o)-objs := $o))
>  $(foreach o,$(filter %.mo,$($1)),$(eval \
>      $o: $($o-objs)))
> -$(eval modules-m += $(patsubst %.o,%.mo,$($1)))
> +$(eval t := $(patsubst %.o,%.mo,$($1)))
> +$(foreach o,$t,$(if $(call is-whitelisted,$o),$(eval \
> +	modules-m += $o)))
>  endef
>  
>  define unnest-vars
> diff --git a/scripts/create_config b/scripts/create_config
> index ecc5d4d..ab430c7 100755
> --- a/scripts/create_config
> +++ b/scripts/create_config
> @@ -37,6 +37,13 @@ case $line in
>   CONFIG_MODULES=*)
>      echo "#define CONFIG_MODULES \"${line#*=}\""
>      ;;
> + CONFIG_MODULE_WHITELIST=*)
> +    echo "#define CONFIG_MODULE_WHITELIST\\"
> +    for mod in ${line#*=}; do
> +      echo "    \"${mod}\",\\"
> +    done
> +    echo "    NULL"
> +    ;;
>   CONFIG_AUDIO_DRIVERS=*)
>      drivers=${line#*=}
>      echo "#define CONFIG_AUDIO_DRIVERS \\"
> diff --git a/util/module.c b/util/module.c
> index 9135c14..cb882f0 100644
> --- a/util/module.c
> +++ b/util/module.c
> @@ -124,7 +124,14 @@ void module_load(module_load_type type)
>      const char *path;
>      char *fname = NULL;
>      DIR *dp;
> +#ifdef CONFIG_MODULE_WHITELIST
> +    const char **mp;
> +    const char *module_whitelist[] = {
> +        CONFIG_MODULE_WHITELIST
> +    };
> +#else
>      struct dirent *ep = NULL;
> +#endif
>  
>      if (!g_module_supported()) {
>          return;
> @@ -149,10 +156,19 @@ void module_load(module_load_type type)
>          fprintf(stderr, "Failed to open dir %s\n", path);
>          return;
>      }
> +#ifdef CONFIG_MODULE_WHITELIST
> +    for (mp = &module_whitelist[0]; *mp; mp++) {
> +        fname = g_strdup_printf("%s%s" HOST_DSOSUF, path, *mp);
> +        module_load_file(fname);
> +        g_free(fname);
> +    }
> +#else
>      for (ep = readdir(dp); ep; ep = readdir(dp)) {
>          fname = g_strdup_printf("%s%s", path, ep->d_name);
>          module_load_file(fname);
>          g_free(fname);
>      }
>  #endif

Having two code paths here is silly. Even if the user does not specify
a whitelist to configure, we know exactly what modules the QEMU source
tree contains. We *never* have any need to use readdir here.

Daniel
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