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[quantal,1/3] isofs: Refuse RW mount of the filesystem instead of making it RO

Message ID 1375259505-32648-2-git-send-email-hui.wang@canonical.com
State New
Headers show

Commit Message

Hui Wang July 31, 2013, 8:31 a.m. UTC 
From: Jan Kara <jack@suse.cz>

The patch is picked from the linux-fsdevel mailing list:
http://marc.info/?l=linux-fsdevel&m=137479131416490&w=2

This patch is going to be merged to linux-3.11

Refuse RW mount of isofs filesystem. So far we just silently changed it
to RO mount but when the media is writeable, block layer won't notice
this change and thus will think device is used RW and will block eject
button of the drive. That is unexpected by users because for
non-writeable media eject button works just fine.

Userspace mount(8) command handles this just fine and retries mounting
with MS_RDONLY set so userspace shouldn't see any regression.  Plus any
tool mounting isofs is likely confronted with the case of read-only
media where block layer already refuses to mount the filesystem without
MS_RDONLY set so our behavior shouldn't be anything new for it.

Reported-by: Hui Wang <hui.wang@canonical.com>
Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/isofs/inode.c | 16 +++++-----------
 1 file changed, 5 insertions(+), 11 deletions(-)
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Patch

diff --git a/fs/isofs/inode.c b/fs/isofs/inode.c
index 29037c3..e92a342 100644
--- a/fs/isofs/inode.c
+++ b/fs/isofs/inode.c
@@ -119,8 +119,8 @@  static void destroy_inodecache(void)
 
 static int isofs_remount(struct super_block *sb, int *flags, char *data)
 {
-	/* we probably want a lot more here */
-	*flags |= MS_RDONLY;
+	if (!(*flags & MS_RDONLY))
+		return -EROFS;
 	return 0;
 }
 
@@ -769,15 +769,6 @@  root_found:
 	 */
 	s->s_maxbytes = 0x80000000000LL;
 
-	/*
-	 * The CDROM is read-only, has no nodes (devices) on it, and since
-	 * all of the files appear to be owned by root, we really do not want
-	 * to allow suid.  (suid or devices will not show up unless we have
-	 * Rock Ridge extensions)
-	 */
-
-	s->s_flags |= MS_RDONLY /* | MS_NODEV | MS_NOSUID */;
-
 	/* Set this for reference. Its not currently used except on write
 	   which we don't have .. */
 
@@ -1536,6 +1527,9 @@  struct inode *isofs_iget(struct super_block *sb,
 static struct dentry *isofs_mount(struct file_system_type *fs_type,
 	int flags, const char *dev_name, void *data)
 {
+	/* We don't support read-write mounts */
+	if (!(flags & MS_RDONLY))
+		return ERR_PTR(-EACCES);
 	return mount_bdev(fs_type, flags, dev_name, data, isofs_fill_super);
 }