Date:   Mon, 17 Oct 2022 23:48:41 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Paul Moore <paul@...l-moore.com>
Cc:     Kees Cook <keescook@...omium.org>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: [PATCH] LSM: Better reporting of actual LSMs at boot

Enhance the details reported by "lsm.debug" in several ways:

- report contents of "security="
- report contents of "CONFIG_LSM"
- report contents of "lsm="
- report any early LSM details
- whitespace-align the output of similar phases for easier visual parsing
- change "disabled" to more accurate "skipped"
- explain what "skipped" and "ignored" mean in a parenthetical

Upgrade the "security= is ignored" warning from pr_info to pr_warn,
and include full arguments list to make the cause even more clear.

Replace static "Security Framework initializing" pr_info with specific
list of the resulting order of enabled LSMs.

Cc: Paul Moore <paul@...l-moore.com>
Cc: James Morris <jmorris@...ei.org>
Cc: "Serge E. Hallyn" <serge@...lyn.com>
Cc: linux-security-module@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 security/security.c | 61 +++++++++++++++++++++++++++++++++++++++------
 1 file changed, 54 insertions(+), 7 deletions(-)

diff --git a/security/security.c b/security/security.c
index 9696dd64095e..6f6079dec270 100644
--- a/security/security.c
+++ b/security/security.c
@@ -159,7 +159,7 @@ static void __init append_ordered_lsm(struct lsm_info *lsm, const char *from)
 		lsm->enabled = &lsm_enabled_true;
 	ordered_lsms[last_lsm++] = lsm;
 
-	init_debug("%s ordering: %s (%sabled)\n", from, lsm->name,
+	init_debug("%s ordered: %s (%sabled)\n", from, lsm->name,
 		   is_enabled(lsm) ? "en" : "dis");
 }
 
@@ -222,7 +222,7 @@ static void __init prepare_lsm(struct lsm_info *lsm)
 	if (enabled) {
 		if ((lsm->flags & LSM_FLAG_EXCLUSIVE) && !exclusive) {
 			exclusive = lsm;
-			init_debug("exclusive chosen: %s\n", lsm->name);
+			init_debug("exclusive chosen:   %s\n", lsm->name);
 		}
 
 		lsm_set_blob_sizes(lsm->blobs);
@@ -250,7 +250,7 @@ static void __init ordered_lsm_parse(const char *order, const char *origin)
 	/* LSM_ORDER_FIRST is always first. */
 	for (lsm = __start_lsm_info; lsm < __end_lsm_info; lsm++) {
 		if (lsm->order == LSM_ORDER_FIRST)
-			append_ordered_lsm(lsm, "first");
+			append_ordered_lsm(lsm, "  first");
 	}
 
 	/* Process "security=", if given. */
@@ -289,7 +289,8 @@ static void __init ordered_lsm_parse(const char *order, const char *origin)
 		}
 
 		if (!found)
-			init_debug("%s ignored: %s\n", origin, name);
+			init_debug("%s ignored: %s (not built into kernel)\n",
+				   origin, name);
 	}
 
 	/* Process "security=", if given. */
@@ -307,7 +308,8 @@ static void __init ordered_lsm_parse(const char *order, const char *origin)
 		if (exists_ordered_lsm(lsm))
 			continue;
 		set_enabled(lsm, false);
-		init_debug("%s disabled: %s\n", origin, lsm->name);
+		init_debug("%s skipped: %s (not in requested order)\n",
+			   origin, lsm->name);
 	}
 
 	kfree(sep);
@@ -318,6 +320,44 @@ static void __init lsm_early_task(struct task_struct *task);
 
 static int lsm_append(const char *new, char **result);
 
+static void __init report_lsm_order(void)
+{
+	struct lsm_info **lsm, *early;
+	size_t size = 0;
+	char *effective, *step, *end;
+
+	/* Count the length of each enabled LSM name. */
+	for (early = __start_early_lsm_info; early < __end_early_lsm_info; early++)
+		if (is_enabled(early))
+			size += strlen(early->name) + 1;
+	for (lsm = ordered_lsms; *lsm; lsm++)
+		if (is_enabled(*lsm))
+			size += strlen((*lsm)->name) + 1;
+
+	/* Allocate space with trailing %NUL or give up. */
+	size += 1;
+	effective = kzalloc(size, GFP_KERNEL);
+	if (!effective)
+		return;
+	end = effective + size;
+	step = effective;
+
+	/* Append each enabled LSM name. */
+	for (early = __start_early_lsm_info; early < __end_early_lsm_info; early++)
+		if (is_enabled(early))
+			step += scnprintf(step, end - step, "%s%s",
+					  step == effective ? "" : ",",
+					  early->name);
+	for (lsm = ordered_lsms; *lsm; lsm++)
+		if (is_enabled(*lsm))
+			step += scnprintf(step, end - step, "%s%s",
+					  step == effective ? "" : ",",
+					  (*lsm)->name);
+
+	pr_info("initializing lsm=%s\n", effective);
+	kfree(effective);
+}
+
 static void __init ordered_lsm_init(void)
 {
 	struct lsm_info **lsm;
@@ -327,7 +367,8 @@ static void __init ordered_lsm_init(void)
 
 	if (chosen_lsm_order) {
 		if (chosen_major_lsm) {
-			pr_info("security= is ignored because it is superseded by lsm=\n");
+			pr_warn("security=%s is ignored because it is superseded by lsm=%s\n",
+				chosen_major_lsm, chosen_lsm_order);
 			chosen_major_lsm = NULL;
 		}
 		ordered_lsm_parse(chosen_lsm_order, "cmdline");
@@ -337,6 +378,8 @@ static void __init ordered_lsm_init(void)
 	for (lsm = ordered_lsms; *lsm; lsm++)
 		prepare_lsm(*lsm);
 
+	report_lsm_order();
+
 	init_debug("cred blob size       = %d\n", blob_sizes.lbs_cred);
 	init_debug("file blob size       = %d\n", blob_sizes.lbs_file);
 	init_debug("inode blob size      = %d\n", blob_sizes.lbs_inode);
@@ -393,13 +436,17 @@ int __init security_init(void)
 {
 	struct lsm_info *lsm;
 
-	pr_info("Security Framework initializing\n");
+	init_debug("legacy security=%s\n", chosen_major_lsm ?: " *unspecified*");
+	init_debug("  CONFIG_LSM=%s\n", builtin_lsm_order);
+	init_debug("boot arg lsm=%s\n", chosen_lsm_order ?: " *unspecified*");
 
 	/*
 	 * Append the names of the early LSM modules now that kmalloc() is
 	 * available
 	 */
 	for (lsm = __start_early_lsm_info; lsm < __end_early_lsm_info; lsm++) {
+		init_debug("  early started: %s (%sabled)\n", lsm->name,
+			   is_enabled(lsm) ? "en" : "dis");
 		if (lsm->enabled)
 			lsm_append(lsm->name, &lsm_names);
 	}
-- 
2.34.1

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