[PATCH V2 1/2] target: fix selinux error when systemd-modules loads the target module

[Maurizio Lombardi <mlombard@redhat.com>]

If the systemd-modules service loads the target module, the credentials
of that userspace process will be used to validate the access to the
target db directory.
selinux will prevent it, reporting an error like the following:

kernel: audit: type=1400 audit(1676301082.205:4): avc: denied  { read }
for  pid=1020 comm="systemd-modules" name="target" dev="dm-3"
ino=4657583 scontext=system_u:system_r:systemd_modules_load_t:s0
tcontext=system_u:object_r:targetd_etc_rw_t:s0 tclass=dir permissive=0

Fix the error by using the kernel credentials to access the db directory

Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
---

v2: call target_xcopy_release_pt() to destroy the xcopy_wq in case of failure

 drivers/target/target_core_configfs.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/target/target_core_configfs.c b/drivers/target/target_core_configfs.c
index a5f58988130a..3f3dd0c0ce8c 100644
--- a/drivers/target/target_core_configfs.c
+++ b/drivers/target/target_core_configfs.c
@@ -3656,6 +3656,8 @@ static int __init target_core_init_configfs(void)
 {
 	struct configfs_subsystem *subsys = &target_core_fabrics;
 	struct t10_alua_lu_gp *lu_gp;
+	struct cred *kern_cred;
+	const struct cred *old_cred;
 	int ret;
 
 	pr_debug("TARGET_CORE[0]: Loading Generic Kernel Storage"
@@ -3732,11 +3734,21 @@ static int __init target_core_init_configfs(void)
 	if (ret < 0)
 		goto out;
 
+	/* We use the kernel credentials to access the target directory */
+	kern_cred = prepare_kernel_cred(&init_task);
+	if (!kern_cred) {
+		ret = -ENOMEM;
+		goto out;
+	}
+	old_cred = override_creds(kern_cred);
 	target_init_dbroot();
+	revert_creds(old_cred);
+	put_cred(kern_cred);
 
 	return 0;
 
 out:
+	target_xcopy_release_pt();
 	configfs_unregister_subsystem(subsys);
 	core_dev_release_virtual_lun0();
 	rd_module_exit();
-- 
2.39.3