---
NOTE: the security_task_fix_setgid line in sys_setfsgid is over 80
characters, but I figured I'd just follow how it was done in sys_setfsuid
rather than trying to wrap the line, since the functions are nearly
identical.

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 8f1131c8dd54..a2166c812a97 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h

@@ -599,6 +599,15 @@

? *@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.

@@ -1587,6 +1596,8 @@ union security_list_options {

?? ? ?enum kernel_read_file_id id);
?int (*task_fix_setuid)(struct cred *new, const struct cred *old,
?int flags);
+int (*task_fix_setgid)(struct cred *new, const struct cred *old,
+int flags);
?int (*task_setpgid)(struct task_struct *p, pid_t pgid);
?int (*task_getpgid)(struct task_struct *p);
?int (*task_getsid)(struct task_struct *p);

@@ -1876,6 +1887,7 @@ struct security_hook_heads {

?struct hlist_head kernel_post_read_file;
?struct hlist_head kernel_module_request;
?struct hlist_head task_fix_setuid;
+struct hlist_head task_fix_setgid;
?struct hlist_head task_setpgid;
?struct hlist_head task_getpgid;
?struct hlist_head task_getsid;

diff --git a/include/linux/security.h b/include/linux/security.h
index 63030c85ee19..a82d97cf13ab 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h

@@ -325,6 +325,8 @@ 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);

@@ -929,6 +931,13 @@ 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 38509dc1f77b..f6ef922c6815 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c

@@ -392,6 +392,10 @@ 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:

@@ -434,6 +438,10 @@ 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:

@@ -755,6 +763,10 @@ 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:

@@ -861,7 +873,8 @@ 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 68f46d849abe..587786fc0aaa 100644
--- a/security/security.c
+++ b/security/security.c

@@ -1062,6 +1062,12 @@ 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);

--
4.18-rc2

--