1 files changed, 32 insertions, 43 deletions

diff --git a/fs/inode.c b/fs/inode.c
index b608528efd3a..f453eb58fd03 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1949,40 +1949,12 @@ skip_update:
 EXPORT_SYMBOL(touch_atime);
 
 /*
- * The logic we want is
- *
- *	if suid or (sgid and xgrp)
- *		remove privs
- */
-int should_remove_suid(struct dentry *dentry)
-{
-	umode_t mode = d_inode(dentry)->i_mode;
-	int kill = 0;
-
-	/* suid always must be killed */
-	if (unlikely(mode & S_ISUID))
-		kill = ATTR_KILL_SUID;
-
-	/*
-	 * sgid without any exec bits is just a mandatory locking mark; leave
-	 * it alone.  If some exec bits are set, it's a real sgid; kill it.
-	 */
-	if (unlikely((mode & S_ISGID) && (mode & S_IXGRP)))
-		kill |= ATTR_KILL_SGID;
-
-	if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode)))
-		return kill;
-
-	return 0;
-}
-EXPORT_SYMBOL(should_remove_suid);
-
-/*
  * Return mask of changes for notify_change() that need to be done as a
  * response to write or truncate. Return 0 if nothing has to be changed.
  * Negative value on error (change should be denied).
  */
-int dentry_needs_remove_privs(struct dentry *dentry)
+int dentry_needs_remove_privs(struct user_namespace *mnt_userns,
+			      struct dentry *dentry)
 {
 	struct inode *inode = d_inode(dentry);
 	int mask = 0;
@@ -1991,7 +1963,7 @@ int dentry_needs_remove_privs(struct dentry *dentry)
 	if (IS_NOSEC(inode))
 		return 0;
 
-	mask = should_remove_suid(dentry);
+	mask = setattr_should_drop_suidgid(mnt_userns, inode);
 	ret = security_inode_need_killpriv(dentry);
 	if (ret < 0)
 		return ret;
@@ -2023,7 +1995,7 @@ static int __file_remove_privs(struct file *file, unsigned int flags)
 	if (IS_NOSEC(inode) || !S_ISREG(inode->i_mode))
 		return 0;
 
-	kill = dentry_needs_remove_privs(dentry);
+	kill = dentry_needs_remove_privs(file_mnt_user_ns(file), dentry);
 	if (kill < 0)
 		return kill;
 
@@ -2071,9 +2043,6 @@ static int inode_needs_update_time(struct inode *inode, struct timespec64 *now)
 	if (IS_I_VERSION(inode) && inode_iversion_need_inc(inode))
 		sync_it |= S_VERSION;
 
-	if (!sync_it)
-		return 0;
-
 	return sync_it;
 }
 
@@ -2354,15 +2323,15 @@ EXPORT_SYMBOL(inode_init_owner);
 bool inode_owner_or_capable(struct user_namespace *mnt_userns,
 			    const struct inode *inode)
 {
-	kuid_t i_uid;
+	vfsuid_t vfsuid;
 	struct user_namespace *ns;
 
-	i_uid = i_uid_into_mnt(mnt_userns, inode);
-	if (uid_eq(current_fsuid(), i_uid))
+	vfsuid = i_uid_into_vfsuid(mnt_userns, inode);
+	if (vfsuid_eq_kuid(vfsuid, current_fsuid()))
 		return true;
 
 	ns = current_user_ns();
-	if (kuid_has_mapping(ns, i_uid) && ns_capable(ns, CAP_FOWNER))
+	if (vfsuid_has_mapping(ns, vfsuid) && ns_capable(ns, CAP_FOWNER))
 		return true;
 	return false;
 }
@@ -2488,6 +2457,28 @@ struct timespec64 current_time(struct inode *inode)
 EXPORT_SYMBOL(current_time);
 
 /**
+ * in_group_or_capable - check whether caller is CAP_FSETID privileged
+ * @mnt_userns: user namespace of the mount @inode was found from
+ * @inode:	inode to check
+ * @vfsgid:	the new/current vfsgid of @inode
+ *
+ * Check wether @vfsgid is in the caller's group list or if the caller is
+ * privileged with CAP_FSETID over @inode. This can be used to determine
+ * whether the setgid bit can be kept or must be dropped.
+ *
+ * Return: true if the caller is sufficiently privileged, false if not.
+ */
+bool in_group_or_capable(struct user_namespace *mnt_userns,
+			 const struct inode *inode, vfsgid_t vfsgid)
+{
+	if (vfsgid_in_group_p(vfsgid))
+		return true;
+	if (capable_wrt_inode_uidgid(mnt_userns, inode, CAP_FSETID))
+		return true;
+	return false;
+}
+
+/**
  * mode_strip_sgid - handle the sgid bit for non-directories
  * @mnt_userns: User namespace of the mount the inode was created from
  * @dir: parent directory inode
@@ -2508,11 +2499,9 @@ umode_t mode_strip_sgid(struct user_namespace *mnt_userns,
 		return mode;
 	if (S_ISDIR(mode) || !dir || !(dir->i_mode & S_ISGID))
 		return mode;
-	if (in_group_p(i_gid_into_mnt(mnt_userns, dir)))
-		return mode;
-	if (capable_wrt_inode_uidgid(mnt_userns, dir, CAP_FSETID))
+	if (in_group_or_capable(mnt_userns, dir,
+				i_gid_into_vfsgid(mnt_userns, dir)))
 		return mode;
-
 	return mode & ~S_ISGID;
 }
 EXPORT_SYMBOL(mode_strip_sgid);