linux-kernel - [PATCH v6 2/4] module: panic: Taint the kernel when selftest modules load

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Date:   Fri,  8 Jul 2022 12:48:45 +0800
From:   David Gow <davidgow@...gle.com>
To:     Brendan Higgins <brendanhiggins@...gle.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Jonathan Corbet <corbet@....net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>
Cc:     David Gow <davidgow@...gle.com>,
        "Guilherme G . Piccoli" <gpiccoli@...lia.com>,
        Sebastian Reichel <sre@...nel.org>,
        John Ogness <john.ogness@...utronix.de>,
        Joe Fradley <joefradley@...gle.com>,
        Daniel Latypov <dlatypov@...gle.com>,
        kunit-dev@...glegroups.com, linux-kselftest@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Lucas De Marchi <lucas.demarchi@...el.com>,
        Aaron Tomlin <atomlin@...hat.com>,
        linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org,
        Michal Marek <michal.lkml@...kovi.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-kbuild@...r.kernel.org
Subject: [PATCH v6 2/4] module: panic: Taint the kernel when selftest modules load

Taint the kernel with TAINT_TEST whenever a test module loads, by adding
a new "TEST" module property, and setting it for all modules in the
tools/testing directory. This property can also be set manually, for
tests which live outside the tools/testing directory with:
MODULE_INFO(test, "Y");

Reviewed-by: Luis Chamberlain <mcgrof@...nel.org>
Reviewed-by: Aaron Tomlin <atomlin@...hat.com>
Acked-by: Brendan Higgins <brendanhiggins@...gle.com>
Signed-off-by: David Gow <davidgow@...gle.com>
---

Version 6 of this patch fixes the issue pointed out by Nathan here,
whereby the check for the module property was inverted:
https://lore.kernel.org/linux-kselftest/Ysd9FG1fOSnzKv8d@dev-arch.thelio-3990X/

Changes since v5:
https://lore.kernel.org/linux-kselftest/20220702040959.3232874-2-davidgow@google.com/
- Fix the test for the module property being inverted, making this patch
  do exactly the opposite of what it should. (Thanks Nathan Chancellor)
- Revert to using pr_warn(), as we already don't warn if the kernel is
  tainted, so won't spam the logs.
- Add Reviewed-, Acked-by tags.

Changes since v4:
https://lore.kernel.org/linux-kselftest/20220701084744.3002019-2-davidgow@google.com/
- Use pr_warn_once() to only log a warning the first time a module
taints the kernel with TAINT_TEST
  - Loading lots of test modules is a common usecase, and this would
otherwise spam the logs too much.
  - Thanks Luis.
- Remove a superfluous newline (Thanks Greg)
- Add Luis' Reviewed-by tag.

This patch was new in v4 of the series.

---
 kernel/module/main.c  | 7 +++++++
 scripts/mod/modpost.c | 3 +++
 2 files changed, 10 insertions(+)

diff --git a/kernel/module/main.c b/kernel/module/main.c
index fed58d30725d..4723f1316709 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -1988,6 +1988,13 @@ static int check_modinfo(struct module *mod, struct load_info *info, int flags)
 	/* Set up license info based on the info section */
 	set_license(mod, get_modinfo(info, "license"));
 
+	if (get_modinfo(info, "test")) {
+		if (!test_taint(TAINT_TEST))
+			pr_warn("%s: loading test module taints kernel.\n",
+				mod->name);
+		add_taint_module(mod, TAINT_TEST, LOCKDEP_STILL_OK);
+	}
+
 	return 0;
 }
 
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 29d5a841e215..5937212b4433 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -2191,6 +2191,9 @@ static void add_header(struct buffer *b, struct module *mod)
 
 	if (strstarts(mod->name, "drivers/staging"))
 		buf_printf(b, "\nMODULE_INFO(staging, \"Y\");\n");
+
+	if (strstarts(mod->name, "tools/testing"))
+		buf_printf(b, "\nMODULE_INFO(test, \"Y\");\n");
 }
 
 static void add_exported_symbols(struct buffer *buf, struct module *mod)
-- 
2.37.0.rc0.161.g10f37bed90-goog