ima: Introduce MMAP_CHECK_REQPROT hook

Commit 98de59bfe4b2f ("take calculation of final prot in
security_mmap_file() into a helper") caused ima_file_mmap() to receive the
protections requested by the application and not those applied by the
kernel.

After restoring the original MMAP_CHECK behavior, existing attestation
servers might be broken due to not being ready to handle new entries
(previously missing) in the IMA measurement list.

Restore the original correct MMAP_CHECK behavior, instead of keeping the
current buggy one and introducing a new hook with the correct behavior.
Otherwise, there would have been the risk of IMA users not noticing the
problem at all, as they would actively have to update the IMA policy, to
switch to the correct behavior.

Also, introduce the new MMAP_CHECK_REQPROT hook to keep the current
behavior, so that IMA users could easily fix a broken attestation server,
although this approach is discouraged due to potentially missing
measurements.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

5 files changed, 32 insertions, 6 deletions

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 03b440921e61..7186769d5e13 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -190,6 +190,7 @@ static inline unsigned int ima_hash_key(u8 *digest)
 	hook(NONE, none)				\
 	hook(FILE_CHECK, file)				\
 	hook(MMAP_CHECK, mmap)				\
+	hook(MMAP_CHECK_REQPROT, mmap_reqprot)		\
 	hook(BPRM_CHECK, bprm)				\
 	hook(CREDS_CHECK, creds)			\
 	hook(POST_SETATTR, post_setattr)		\
diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
index 1e3a7a4f8833..635803b0d522 100644
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -179,7 +179,8 @@ err_out:
  *		subj=, obj=, type=, func=, mask=, fsmagic=
  *	subj,obj, and type: are LSM specific.
  *	func: FILE_CHECK | BPRM_CHECK | CREDS_CHECK | MMAP_CHECK | MODULE_CHECK
- *	| KEXEC_CMDLINE | KEY_CHECK | CRITICAL_DATA
+ *	| KEXEC_CMDLINE | KEY_CHECK | CRITICAL_DATA | SETXATTR_CHECK
+ *	| MMAP_CHECK_REQPROT
  *	mask: contains the permission mask
  *	fsmagic: hex value
  *
diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index ee6f7e237f2e..97c7d247315c 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -111,6 +111,7 @@ enum integrity_status ima_get_cache_status(struct integrity_iint_cache *iint,
 {
 	switch (func) {
 	case MMAP_CHECK:
+	case MMAP_CHECK_REQPROT:
 		return iint->ima_mmap_status;
 	case BPRM_CHECK:
 		return iint->ima_bprm_status;
@@ -131,6 +132,7 @@ static void ima_set_cache_status(struct integrity_iint_cache *iint,
 {
 	switch (func) {
 	case MMAP_CHECK:
+	case MMAP_CHECK_REQPROT:
 		iint->ima_mmap_status = status;
 		break;
 	case BPRM_CHECK:
@@ -155,6 +157,7 @@ static void ima_cache_flags(struct integrity_iint_cache *iint,
 {
 	switch (func) {
 	case MMAP_CHECK:
+	case MMAP_CHECK_REQPROT:
 		iint->flags |= (IMA_MMAP_APPRAISED | IMA_APPRAISED);
 		break;
 	case BPRM_CHECK:
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 3948e54421cf..31ab86f7e4d3 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -89,7 +89,8 @@ static int mmap_violation_check(enum ima_hooks func, struct file *file,
 	struct inode *inode;
 	int rc = 0;
 
-	if ((func == MMAP_CHECK) && mapping_writably_mapped(file->f_mapping)) {
+	if ((func == MMAP_CHECK || func == MMAP_CHECK_REQPROT) &&
+	    mapping_writably_mapped(file->f_mapping)) {
 		rc = -ETXTBSY;
 		inode = file_inode(file);
 
@@ -227,7 +228,8 @@ static int process_measurement(struct file *file, const struct cred *cred,
 	action = ima_get_action(file_mnt_user_ns(file), inode, cred, secid,
 				mask, func, &pcr, &template_desc, NULL,
 				&allowed_algos);
-	violation_check = ((func == FILE_CHECK || func == MMAP_CHECK) &&
+	violation_check = ((func == FILE_CHECK || func == MMAP_CHECK ||
+			    func == MMAP_CHECK_REQPROT) &&
 			   (ima_policy_flag & IMA_MEASURE));
 	if (!action && !violation_check)
 		return 0;
@@ -411,12 +413,23 @@ int ima_file_mmap(struct file *file, unsigned long reqprot,
 		  unsigned long prot, unsigned long flags)
 {
 	u32 secid;
+	int ret;
 
-	if (file && (prot & PROT_EXEC)) {
-		security_current_getsecid_subj(&secid);
+	if (!file)
+		return 0;
+
+	security_current_getsecid_subj(&secid);
+
+	if (reqprot & PROT_EXEC) {
+		ret = process_measurement(file, current_cred(), secid, NULL,
+					  0, MAY_EXEC, MMAP_CHECK_REQPROT);
+		if (ret)
+			return ret;
+	}
+
+	if (prot & PROT_EXEC)
 		return process_measurement(file, current_cred(), secid, NULL,
 					   0, MAY_EXEC, MMAP_CHECK);
-	}
 
 	return 0;
 }
@@ -457,6 +470,10 @@ int ima_file_mprotect(struct vm_area_struct *vma, unsigned long prot)
 	action = ima_get_action(file_mnt_user_ns(vma->vm_file), inode,
 				current_cred(), secid, MAY_EXEC, MMAP_CHECK,
 				&pcr, &template, NULL, NULL);
+	action |= ima_get_action(file_mnt_user_ns(vma->vm_file), inode,
+				 current_cred(), secid, MAY_EXEC,
+				 MMAP_CHECK_REQPROT, &pcr, &template, NULL,
+				 NULL);
 
 	/* Is the mmap'ed file in policy? */
 	if (!(action & (IMA_MEASURE | IMA_APPRAISE_SUBMASK)))
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index a8b9a1387a21..40c0769238e6 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -697,6 +697,7 @@ static int get_subaction(struct ima_rule_entry *rule, enum ima_hooks func)
 
 	switch (func) {
 	case MMAP_CHECK:
+	case MMAP_CHECK_REQPROT:
 		return IMA_MMAP_APPRAISE;
 	case BPRM_CHECK:
 		return IMA_BPRM_APPRAISE;
@@ -1266,6 +1267,7 @@ static bool ima_validate_rule(struct ima_rule_entry *entry)
 	case NONE:
 	case FILE_CHECK:
 	case MMAP_CHECK:
+	case MMAP_CHECK_REQPROT:
 	case BPRM_CHECK:
 	case CREDS_CHECK:
 	case POST_SETATTR:
@@ -1504,6 +1506,8 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
 			else if ((strcmp(args[0].from, "FILE_MMAP") == 0)
 				|| (strcmp(args[0].from, "MMAP_CHECK") == 0))
 				entry->func = MMAP_CHECK;
+			else if ((strcmp(args[0].from, "MMAP_CHECK_REQPROT") == 0))
+				entry->func = MMAP_CHECK_REQPROT;
 			else if (strcmp(args[0].from, "BPRM_CHECK") == 0)
 				entry->func = BPRM_CHECK;
 			else if (strcmp(args[0].from, "CREDS_CHECK") == 0)