Merge tag 'fs.setgid.v6.0' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner...

[linux-2.6-microblaze.git] / fs / inode.c

diff --git a/fs/inode.c b/fs/inode.c
index 524ee91..9c3cd54 100644 (file)
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -2326,10 +2326,6 @@ void inode_init_owner(struct user_namespace *mnt_userns, struct inode *inode,
                /* Directories are special, and always inherit S_ISGID */
                if (S_ISDIR(mode))
                        mode |= S_ISGID;
-               else if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP) &&
-                        !in_group_p(i_gid_into_mnt(mnt_userns, dir)) &&
-                        !capable_wrt_inode_uidgid(mnt_userns, dir, CAP_FSETID))
-                       mode &= ~S_ISGID;
        } else
                inode_fsgid_set(inode, mnt_userns);
        inode->i_mode = mode;
@@ -2485,3 +2481,33 @@ struct timespec64 current_time(struct inode *inode)
        return timestamp_truncate(now, inode);
 }
 EXPORT_SYMBOL(current_time);
+
+/**
+ * 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
+ * @mode: mode of the file to be created in @dir
+ *
+ * If the @mode of the new file has both the S_ISGID and S_IXGRP bit
+ * raised and @dir has the S_ISGID bit raised ensure that the caller is
+ * either in the group of the parent directory or they have CAP_FSETID
+ * in their user namespace and are privileged over the parent directory.
+ * In all other cases, strip the S_ISGID bit from @mode.
+ *
+ * Return: the new mode to use for the file
+ */
+umode_t mode_strip_sgid(struct user_namespace *mnt_userns,
+                       const struct inode *dir, umode_t mode)
+{
+       if ((mode & (S_ISGID | S_IXGRP)) != (S_ISGID | S_IXGRP))
+               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))
+               return mode;
+
+       return mode & ~S_ISGID;
+}
+EXPORT_SYMBOL(mode_strip_sgid);