Merge tag 'LSM-add-setgid-hook-5.8-author-fix' of git://github.com/micah-morton/linux

Pull SafeSetID update from Micah Morton:
 "Add additional LSM hooks for SafeSetID

  SafeSetID is capable of making allow/deny decisions for set*uid calls
  on a system, and we want to add similar functionality for set*gid
  calls.

  The work to do that is not yet complete, so probably won't make it in
  for v5.8, but we are looking to get this simple patch in for v5.8
  since we have it ready.

  We are planning on the rest of the work for extending the SafeSetID
  LSM being merged during the v5.9 merge window"

* tag 'LSM-add-setgid-hook-5.8-author-fix' of git://github.com/micah-morton/linux:
  security: Add LSM hooks to set*gid syscalls

5 files changed, 40 insertions, 1 deletions

diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 4a3d70baa7f1..6791813cd439 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -191,6 +191,8 @@ LSM_HOOK(int, 0, kernel_post_read_file, struct file *file, char *buf,
 	 loff_t size, enum kernel_read_file_id id)
 LSM_HOOK(int, 0, task_fix_setuid, struct cred *new, const struct cred *old,
 	 int flags)
+LSM_HOOK(int, 0, task_fix_setgid, struct cred *new, const struct cred * old,
+	 int flags)
 LSM_HOOK(int, 0, task_setpgid, struct task_struct *p, pid_t pgid)
 LSM_HOOK(int, 0, task_getpgid, struct task_struct *p)
 LSM_HOOK(int, 0, task_getsid, struct task_struct *p)
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 73d87955e26b..95b7c1d32062 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -659,6 +659,15 @@
  *	@old is the set of credentials that are being replaces
  *	@flags contains one of the LSM_SETID_* values.
  *	Return 0 on success.
+ * @task_fix_setgid:
+ *	Update the module's state after setting one or more of the group
+ *	identity attributes of the current process.  The @flags parameter
+ *	indicates which of the set*gid system calls invoked this hook.
+ *	@new is the set of credentials that will be installed.  Modifications
+ *	should be made to this rather than to @current->cred.
+ *	@old is the set of credentials that are being replaced.
+ *	@flags contains one of the LSM_SETID_* values.
+ *	Return 0 on success.
  * @task_setpgid:
  *	Check permission before setting the process group identifier of the
  *	process @p to @pgid.
diff --git a/include/linux/security.h b/include/linux/security.h
index 469fa91f8cf8..0a0a03b36a3b 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -392,6 +392,8 @@ int security_kernel_post_read_file(struct file *file, char *buf, loff_t size,
 				   enum kernel_read_file_id id);
 int security_task_fix_setuid(struct cred *new, const struct cred *old,
 			     int flags);
+int security_task_fix_setgid(struct cred *new, const struct cred *old,
+			     int flags);
 int security_task_setpgid(struct task_struct *p, pid_t pgid);
 int security_task_getpgid(struct task_struct *p);
 int security_task_getsid(struct task_struct *p);
@@ -1036,6 +1038,13 @@ static inline int security_task_fix_setuid(struct cred *new,
 	return cap_task_fix_setuid(new, old, flags);
 }
 
+static inline int security_task_fix_setgid(struct cred *new,
+					   const struct cred *old,
+					   int flags)
+{
+	return 0;
+}
+
 static inline int security_task_setpgid(struct task_struct *p, pid_t pgid)
 {
 	return 0;
diff --git a/kernel/sys.c b/kernel/sys.c
index fd46865b46ba..00a96746e28a 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -393,6 +393,10 @@ long __sys_setregid(gid_t rgid, gid_t egid)
 		new->sgid = new->egid;
 	new->fsgid = new->egid;
 
+	retval = security_task_fix_setgid(new, old, LSM_SETID_RE);
+	if (retval < 0)
+		goto error;
+
 	return commit_creds(new);
 
 error:
@@ -435,6 +439,10 @@ long __sys_setgid(gid_t gid)
 	else
 		goto error;
 
+	retval = security_task_fix_setgid(new, old, LSM_SETID_ID);
+	if (retval < 0)
+		goto error;
+
 	return commit_creds(new);
 
 error:
@@ -756,6 +764,10 @@ long __sys_setresgid(gid_t rgid, gid_t egid, gid_t sgid)
 		new->sgid = ksgid;
 	new->fsgid = new->egid;
 
+	retval = security_task_fix_setgid(new, old, LSM_SETID_RES);
+	if (retval < 0)
+		goto error;
+
 	return commit_creds(new);
 
 error:
@@ -862,7 +874,8 @@ long __sys_setfsgid(gid_t gid)
 	    ns_capable(old->user_ns, CAP_SETGID)) {
 		if (!gid_eq(kgid, old->fsgid)) {
 			new->fsgid = kgid;
-			goto change_okay;
+			if (security_task_fix_setgid(new,old,LSM_SETID_FS) == 0)
+				goto change_okay;
 		}
 	}
 
diff --git a/security/security.c b/security/security.c
index 2a652e59c413..0ce3e73edd42 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1696,6 +1696,12 @@ int security_task_fix_setuid(struct cred *new, const struct cred *old,
 	return call_int_hook(task_fix_setuid, 0, new, old, flags);
 }
 
+int security_task_fix_setgid(struct cred *new, const struct cred *old,
+				 int flags)
+{
+	return call_int_hook(task_fix_setgid, 0, new, old, flags);
+}
+
 int security_task_setpgid(struct task_struct *p, pid_t pgid)
 {
 	return call_int_hook(task_setpgid, 0, p, pgid);