Re: [PATCH 1/5] initmpfs: replace MS_NOUSER in initramfs
From: Eric W. Biederman <hidden>
Date: 2013-06-30 01:16:18
Rob Landley [off-list ref] writes:
From: Rob Landley <redacted> Mounting MS_NOUSER prevents --bind mounts from rootfs. Prevent new rootfs mounts with a different mechanism that doesn't affect bind mounts.
I don't see patches 4 and 5 so I don't know if you have covered this elsewhere but a very important part of the reason for MS_NOUSER is to prevent unmounting of rootfs. The entire vfs breaks if you are allowed to unmount rootfs, and it appears this patch is allowing that. Eric
quoted hunk
Signed-off-by: Rob Landley <redacted> --- fs/ramfs/inode.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)diff --git a/fs/ramfs/inode.c b/fs/ramfs/inode.c index c24f1e1..14b9c35 100644 --- a/fs/ramfs/inode.c +++ b/fs/ramfs/inode.c@@ -247,7 +247,14 @@ struct dentry *ramfs_mount(struct file_system_type *fs_type, static struct dentry *rootfs_mount(struct file_system_type *fs_type, int flags, const char *dev_name, void *data) { - return mount_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super); + static int once; + + if (once) + return ERR_PTR(-ENODEV); + else + once++; + + return mount_nodev(fs_type, flags, data, ramfs_fill_super); } static void ramfs_kill_sb(struct super_block *sb)