Merge branch 'next-integrity' of git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity into next-integrity

From Mimi:

In Linux 4.19, a new LSM hook named security_kernel_load_data was
upstreamed, allowing LSMs and IMA to prevent the kexec_load
syscall.  Different signature verification methods exist for verifying
the kexec'ed kernel image.  This pull request adds additional support
in IMA to prevent loading unsigned kernel images via the kexec_load
syscall, independently of the IMA policy rules, based on the runtime
"secure boot" flag.  An initial IMA kselftest is included.

In addition, this pull request defines a new, separate keyring named
".platform" for storing the preboot/firmware keys needed for verifying
the kexec'ed kernel image's signature and includes the associated IMA
kexec usage of the ".platform" keyring.

(David Howell's and Josh Boyer's patches for reading the
preboot/firmware keys, which were previously posted for a different
use case scenario, are included here.)

1 files changed, 14 insertions, 7 deletions

diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index adaf96932237..043a09189df1 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -105,7 +105,7 @@ static void ima_rdwr_violation_check(struct file *file,
 	} else {
 		if (must_measure)
 			set_bit(IMA_MUST_MEASURE, &iint->atomic_flags);
-		if ((atomic_read(&inode->i_writecount) > 0) && must_measure)
+		if (inode_is_open_for_write(inode) && must_measure)
 			send_writers = true;
 	}
 
@@ -507,20 +507,26 @@ int ima_post_read_file(struct file *file, void *buf, loff_t size,
  */
 int ima_load_data(enum kernel_load_data_id id)
 {
-	bool sig_enforce;
+	bool ima_enforce, sig_enforce;
 
-	if ((ima_appraise & IMA_APPRAISE_ENFORCE) != IMA_APPRAISE_ENFORCE)
-		return 0;
+	ima_enforce =
+		(ima_appraise & IMA_APPRAISE_ENFORCE) == IMA_APPRAISE_ENFORCE;
 
 	switch (id) {
 	case LOADING_KEXEC_IMAGE:
-		if (ima_appraise & IMA_APPRAISE_KEXEC) {
+		if (IS_ENABLED(CONFIG_KEXEC_VERIFY_SIG)
+		    && arch_ima_get_secureboot()) {
+			pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file_load syscall.\n");
+			return -EACCES;
+		}
+
+		if (ima_enforce && (ima_appraise & IMA_APPRAISE_KEXEC)) {
 			pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file_load syscall.\n");
 			return -EACCES;	/* INTEGRITY_UNKNOWN */
 		}
 		break;
 	case LOADING_FIRMWARE:
-		if (ima_appraise & IMA_APPRAISE_FIRMWARE) {
+		if (ima_enforce && (ima_appraise & IMA_APPRAISE_FIRMWARE)) {
 			pr_err("Prevent firmware sysfs fallback loading.\n");
 			return -EACCES;	/* INTEGRITY_UNKNOWN */
 		}
@@ -528,7 +534,8 @@ int ima_load_data(enum kernel_load_data_id id)
 	case LOADING_MODULE:
 		sig_enforce = is_module_sig_enforced();
 
-		if (!sig_enforce && (ima_appraise & IMA_APPRAISE_MODULES)) {
+		if (ima_enforce && (!sig_enforce
+				    && (ima_appraise & IMA_APPRAISE_MODULES))) {
 			pr_err("impossible to appraise a module without a file descriptor. sig_enforce kernel parameter might help\n");
 			return -EACCES;	/* INTEGRITY_UNKNOWN */
 		}