[PATCH 2/2] ima: don't measure/appraise files on configfs

[Frederick Lawler <fred@cloudflare.com>]

When IMA appraises/measures a file configfs, it has an opportunity to
hold onto the ima_iint_mutex while another file from a different file
system is attempting to appraise/measure. This may cause a cyclical
lock dependency.

Add configfs to the default don't measure/appraise lists, similarly to
other pseudo file systems.

Reported-by: syzbot+448c2e24b1ceff13ed2a@syzkaller.appspotmail.com
Link: https://lore.kernel.org/all/6a77c7cd.b50370da.49fe0.0031.GAE@google.com/
Suggested-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Frederick Lawler <fred@cloudflare.com>
---
 security/integrity/ima/ima_policy.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index f79d07bb63c6fc4ba6fe594140de8d59f57e4f0b..68d9a5e6c232ea0678e9f51f105cebecccccb43e 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -165,7 +165,10 @@ static struct ima_rule_entry dont_measure_rules[] __ro_after_init = {
 	{.action = DONT_MEASURE, .fsmagic = CGROUP2_SUPER_MAGIC,
 	 .flags = IMA_FSMAGIC},
 	{.action = DONT_MEASURE, .fsmagic = NSFS_MAGIC, .flags = IMA_FSMAGIC},
-	{.action = DONT_MEASURE, .fsmagic = EFIVARFS_MAGIC, .flags = IMA_FSMAGIC}
+	{.action = DONT_MEASURE, .fsmagic = EFIVARFS_MAGIC,
+	 .flags = IMA_FSMAGIC},
+	{.action = DONT_MEASURE, .fsmagic = CONFIGFS_MAGIC,
+	 .flags = IMA_FSMAGIC}
 };
 
 static struct ima_rule_entry original_measurement_rules[] __ro_after_init = {
@@ -211,6 +214,8 @@ static struct ima_rule_entry default_appraise_rules[] __ro_after_init = {
 	{.action = DONT_APPRAISE, .fsmagic = EFIVARFS_MAGIC, .flags = IMA_FSMAGIC},
 	{.action = DONT_APPRAISE, .fsmagic = CGROUP_SUPER_MAGIC, .flags = IMA_FSMAGIC},
 	{.action = DONT_APPRAISE, .fsmagic = CGROUP2_SUPER_MAGIC, .flags = IMA_FSMAGIC},
+	{.action = DONT_APPRAISE, .fsmagic = CONFIGFS_MAGIC,
+	 .flags = IMA_FSMAGIC},
 #ifdef CONFIG_IMA_WRITE_POLICY
 	{.action = APPRAISE, .func = POLICY_CHECK,
 	.flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},

-- 
2.43.0