commit 270259602236f99a9d737522f383ce45b1ad6a64
Author: Erez_Zadok <[EMAIL PROTECTED]>
Date: Mon Apr 30 16:42:30 2007 -0400
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).
diff --git a/fs/unionfs/super.c b/fs/unionfs/super.c
index 10520c0..3a8d74c 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
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