Messages in this thread | | | From | (Eric W. Biederman) | Date | Sat, 29 Jun 2013 18:15:40 -0700 | Subject | Re: [PATCH 1/5] initmpfs: replace MS_NOUSER in initramfs |
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Rob Landley <rob@landley.net> writes:
> From: Rob Landley <rob@landley.net> > > 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
> Signed-off-by: Rob Landley <rob@landley.net> > --- > > 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)
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