modules: Add kernel parameter to blacklist modules

Blacklisting a module in linux has long been a problem. The current procedure is to use rd.blacklist=module_name, however, that doesn't cover the case after the initramfs and before a boot prompt (where one is supposed to use /etc/modprobe.d/blacklist.conf to blacklist runtime loading). Using rd.shell to get an early prompt is hit-or-miss, and doesn't cover all situations AFAICT. This patch adds this functionality of permanently blacklisting a module by its name via the kernel parameter module_blacklist=module_name. [v2]: Rusty, use core_param() instead of __setup() which simplifies things. [v3]: Rusty, undo wreckage from strsep() [v4]: Rusty, simpler version of blacklisted() Signed-off-by: Prarit Bhargava <[email protected]> Cc: Jonathan Corbet <[email protected]> Cc: Rusty Russell <[email protected]> Cc: [email protected] Signed-off-by: Rusty Russell <[email protected]>
TechNexion · Aug 4, 2016 · be7de5f · be7de5f
1 parent 9502514
commit be7de5f
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diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
@@ -2301,6 +2301,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			Note that if CONFIG_MODULE_SIG_FORCE is set, that
 			is always true, so this option does nothing.
 
+	module_blacklist=  [KNL] Do not load a comma-separated list of
+			modules.  Useful for debugging problem modules.
+
 	mousedev.tap_time=
 			[MOUSE] Maximum time between finger touching and
 			leaving touchpad surface for touch to be considered

diff --git a/kernel/module.c b/kernel/module.c
@@ -3168,6 +3168,27 @@ int __weak module_frob_arch_sections(Elf_Ehdr *hdr,
 	return 0;
 }
 
+/* module_blacklist is a comma-separated list of module names */
+static char *module_blacklist;
+static bool blacklisted(char *module_name)
+{
+	const char *p;
+	size_t len;
+
+	if (!module_blacklist)
+		return false;
+
+	for (p = module_blacklist; *p; p += len) {
+		len = strcspn(p, ",");
+		if (strlen(module_name) == len && !memcmp(module_name, p, len))
+			return true;
+		if (p[len] == ',')
+			len++;
+	}
+	return false;
+}
+core_param(module_blacklist, module_blacklist, charp, 0400);
+
 static struct module *layout_and_allocate(struct load_info *info, int flags)
 {
 	/* Module within temporary copy. */
@@ -3178,6 +3199,9 @@ static struct module *layout_and_allocate(struct load_info *info, int flags)
 	if (IS_ERR(mod))
 		return mod;
 
+	if (blacklisted(mod->name))
+		return ERR_PTR(-EPERM);
+
 	err = check_modinfo(mod, info, flags);
 	if (err)
 		return ERR_PTR(err);