[PATCH] libkmod: introduce kmod_module_uniq_options() to improve the reliability of loading module

[Wen Yang <wenyang@linux.alibaba.com>]

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@linux.alibaba.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Lucas De Marchi <lucas.de.marchi@gmail.com>
Cc: Topi Miettinen <toiwoton@gmail.com>
Cc: Alexey Gladkov <gladkov.alexey@gmail.com>
Cc: linux-modules@vger.kernel.org
---
 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;
+	     tok = strtok_r(NULL, " ", &saveptr), nr_opts++) {}
+
+	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);
+	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