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Subject[PATCH v3] Add kernel parameter to blacklist modules
Date
Rusty?  Didn't see anything from you on this ... resending.

P.


----8<----

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()

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: linux-doc@vger.kernel.org
---
Documentation/kernel-parameters.txt | 3 +++
kernel/module.c | 29 +++++++++++++++++++++++++++++
2 files changed, 32 insertions(+)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 82b42c958d1c..c720b96f2efc 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2295,6 +2295,9 @@ 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
index 5f71aa63ed2a..5240da88af79 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -3155,6 +3155,32 @@ 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)
+{
+ char *str, *entry;
+
+ if (!module_blacklist)
+ return false;
+
+ str = module_blacklist;
+ do {
+ if (str != module_blacklist)
+ module_blacklist[strlen(str) - 1] = ',';
+ entry = strsep(&str, ",");
+ if (!strcmp(module_name, entry)) {
+ pr_info("module %s is blacklisted\n", module_name);
+ if (str != module_blacklist)
+ module_blacklist[strlen(str) - 1] = ',';
+ return true;
+ }
+ } while (str);
+
+ 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. */
@@ -3165,6 +3191,9 @@ 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);
--
1.7.9.3
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