On Wed, Apr 29, 2020 at 11:52:08PM +0800, Wen Yang wrote:
> As in commit 2045cdfa1b40 ("netfilter: nf_conntrack: Fix possible possible crash on module loading"),
> Loading the nf_conntrack module with doubled hashsize parameter, i.e.
> modprobe nf_conntrack hashsize=12345 hashsize=12345
> causes NULL-ptr deref.
>
> If 'hashsize' specified twice, the nf_conntrack_set_hashsize() function
> will be called also twice.
>
> In addition, we may also construct the doubled hashsize parameter scenario by using the following configuration:
>
> $ cat /etc/modprobe.d/firewalld-sysctls.conf
> install nf_conntrack /usr/sbin/modprobe --ignore-install nf_conntrack $CMDLINE_OPTS && /usr/sbin/sysctl --quiet --pattern 'net[.]netfilter[.]nf_conntrack.*' --system
>
> $ cat /etc/modprobe.d/nf_conntrack.conf
> options nf_conntrack hashsize=187600
>
> $ sudo modprobe nf_conntrack -v
> install /usr/sbin/modprobe --ignore-install nf_conntrack $CMDLINE_OPTS && /usr/sbin/sysctl --quiet --pattern 'net[.]netfilter[.]nf_conntrack.*' --system hashsize=187500
> insmod /path/to/nf_conntrack.ko hashsize=187500 hashsize=187500
>
> Passing multiple repeated parameters to the kernel may trigger kernel bugs
> and affect the performance of loading kernel modules.
>
> We introduce the nf_conntrack_set_hashsize() and hope to solve this problem.
>
> Signed-off-by: Wen Yang <wenyang@xxxxxxxxxxxxxxxxx>
> Cc: Lucas De Marchi <lucas.demarchi@xxxxxxxxx>
> Cc: Lucas De Marchi <lucas.de.marchi@xxxxxxxxx>
> Cc: Topi Miettinen <toiwoton@xxxxxxxxx>
> Cc: Alexey Gladkov <gladkov.alexey@xxxxxxxxx>
> Cc: linux-modules@xxxxxxxxxxxxxxx
> ---
> libkmod/libkmod-module.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++++
> libkmod/libkmod.h | 1 +
> tools/insmod.c | 7 +++++
> 3 files changed, 80 insertions(+)
>
> diff --git a/libkmod/libkmod-module.c b/libkmod/libkmod-module.c
> index 76a6dc3..f42beb8 100644
> --- a/libkmod/libkmod-module.c
> +++ b/libkmod/libkmod-module.c
> @@ -1076,6 +1076,72 @@ static char *module_options_concat(const char *opt, const char *xopt)
> return r;
> }
>
> +static unsigned int module_options_cnt(const char *opts)
> +{
> + int nr_opts = 0;
> + char *saveptr, *tok, *buf;
> +
> + if (!opts)
> + return 0;
> +
> + buf = strdup(opts);
> + for (tok = strtok_r(buf, " ", &saveptr); tok != NULL;
Why not use strchr() to find the " " and count them ?
> + tok = strtok_r(NULL, " ", &saveptr), nr_opts++) {}
> +
Parameters can have spaces [1]. Is not it so ?
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/lib/cmdline.c#n196
> + free(buf);
> + return nr_opts;
> +}
> +
> +KMOD_EXPORT int kmod_module_uniq_options(char **opts)
> +{
> + char *buf;
> + char **array;
> + bool duplicated;
> + char *saveptr, *tok;
> + int nr_opts, len, i, j;
> +
> + if (!opts || !*opts)
> + return 0;
> +
> + buf = strdup(*opts);
We have the options passed as an argument. You doubled it here and tripled
in the module_options_cnt(). Can you reduce memory usage ?
> + if (!buf)
> + return -ENOMEM;
> +
> + len = strlen(buf);
> + nr_opts = module_options_cnt(buf);
> + array = calloc(nr_opts, sizeof(char *));
> + if (!buf)
> + return -ENOMEM;
> +
> + for (tok = strtok_r(buf, " ", &saveptr), i = 0; tok != NULL;
> + tok = strtok_r(NULL, " ", &saveptr), i++) {
> + array[i] = tok;
> + }
> +
> + (*opts)[0] = '\0';
> + len = 0;
> + for (i = 0; i < nr_opts; i++) {
> + duplicated = false;
> + for (j = 0; j < i; j++) {
> + if (strcmp(array[i], array[j]) == 0) {
> + duplicated = true;
> + break;
> + }
> + }
> +
> + if (!duplicated) {
> + strcat(*opts, array[i]);
> + strcat(*opts, " ");
> + len += strlen(array[i]) + 1;
> + }
> + }
> +
> + (*opts)[len] = '\0';
> + free(buf);
> + free(array);
> + return 0;
> +}
> +
> static int __kmod_module_get_probe_list(struct kmod_module *mod,
> bool required,
> bool ignorecmd,
> @@ -1322,6 +1388,12 @@ KMOD_EXPORT int kmod_module_probe_insert_module(struct kmod_module *mod,
> options = module_options_concat(moptions,
> m == mod ? extra_options : NULL);
>
> + err = kmod_module_uniq_options(&options);
> + if (err < 0) {
> + free(options);
> + return err;
> + }
> +
> if (cmd != NULL && !m->ignorecmd) {
> if (print_action != NULL)
> print_action(m, true, options ?: "");
> diff --git a/libkmod/libkmod.h b/libkmod/libkmod.h
> index 3cab2e5..774e52a 100644
> --- a/libkmod/libkmod.h
> +++ b/libkmod/libkmod.h
> @@ -186,6 +186,7 @@ int kmod_module_probe_insert_module(struct kmod_module *mod,
> const char *kmod_module_get_name(const struct kmod_module *mod);
> const char *kmod_module_get_path(const struct kmod_module *mod);
> const char *kmod_module_get_options(const struct kmod_module *mod);
> +int kmod_module_uniq_options(char **opts);
> const char *kmod_module_get_install_commands(const struct kmod_module *mod);
> const char *kmod_module_get_remove_commands(const struct kmod_module *mod);
> struct kmod_list *kmod_module_get_dependencies(const struct kmod_module *mod);
> diff --git a/tools/insmod.c b/tools/insmod.c
> index c422971..2dc0c22 100644
> --- a/tools/insmod.c
> +++ b/tools/insmod.c
> @@ -132,6 +132,13 @@ static int do_insmod(int argc, char *argv[])
> opts[optslen] = '\0';
> }
>
> + err = kmod_module_uniq_options(&opts);
> + if (err < 0) {
> + ERR("kmod_module_uniq_options() failed!\n");
> + free(opts);
> + return err;
> + }
> +
> ctx = kmod_new(NULL, &null_config);
> if (!ctx) {
> ERR("kmod_new() failed!\n");
> --
> 1.8.3.1
>
--
Rgrds, legion
