From 7f3d6562e0a55c2a146dd78bc3dbed01b858201e Mon Sep 17 00:00:00 2001 From: Erez_Zadok Date: Mon, 30 Apr 2007 16:42:30 -0400 Subject: [PATCH] branch management: disallow setting leftmost branch to readonly Unionfs requires the leftmost branch to be writeable for copyup to work properly and simply. If, through branch-management commands (add, delete, or mode change), the leftmost branch will becomes readonly, then return an error (and tell the user to use "remount,ro" if they want a readonly union). --- fs/unionfs/super.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/fs/unionfs/super.c b/fs/unionfs/super.c index 10520c0fbf39..3a8d74c53955 100644 --- a/fs/unionfs/super.c +++ b/fs/unionfs/super.c @@ -626,12 +626,20 @@ static int unionfs_remount_fs(struct super_block *sb, int *flags, out_no_change: /****************************************************************** - * WE'RE ALMOST DONE: see if we need to allocate a small-sized new - * vector, copy the vectors to their correct place, release the - * refcnt of the older ones, and return. - * Also handle invalidating any pages that will have to be re-read. + * WE'RE ALMOST DONE: check if leftmost branch might be read-only, + * see if we need to allocate a small-sized new vector, copy the + * vectors to their correct place, release the refcnt of the older + * ones, and return. Also handle invalidating any pages that will + * have to be re-read. *******************************************************************/ + if (!(tmp_data[0].branchperms & MAY_WRITE)) { + printk("unionfs: leftmost branch cannot be read-only " + "(use \"remount,ro\" to create a read-only union)\n"); + err = -EINVAL; + goto out_release; + } + /* * Allocate space for actual pointers, if needed. By the time we * finish this block of code, new_branches and new_lower_paths will -- 2.43.0