Re: [PATCH 2/2] debugfs: only allow root access to debugging interfaces

[David Daney]

On 02/22/2011 10:16 AM, Kees Cook wrote:
> Har har, I forgot --compose to "git send-email".
>
> Anyway, with the continuing deluge of bugs in the "debug" filesystem, I
> would like to make that filesystem's root directory mode 0700 by default
> since it's filled with crazy stuff that regular users do not need to see.
>
> Better to try to just close the door completely on all the stuff in there.
> It is, after all, supposed to only be used for debugging, right?

It depends if you consider use of ftrace and kprobes 'debugging'.  In 
any event, you really have to be root to be able to manipulate them.

I can currently do 'cat /sys/kernel/debug/tracing/trace' as a normal 
user.  With your change I don't think it would be possible.  This is not 
something I often (ever) do, but it is a change.

David Daney


> -Kees
>
> On Tue, Feb 22, 2011 at 10:09:58AM -0800, Kees Cook wrote:
> > Block access to the potentially dangerous debugging interfaces in
> > the debugfs filesystem.
> >
> > Signed-off-by: Kees Cook<kees.cook@xxxxxxxxxxxxx>
> > ---
> >   fs/debugfs/inode.c |    2 +-
> >   1 files changed, 1 insertions(+), 1 deletions(-)
> >
> > diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
> > index 3cb33c3..83c61a3 100644
> > --- a/fs/debugfs/inode.c
> > +++ b/fs/debugfs/inode.c
> > @@ -133,7 +133,7 @@ static int debug_fill_super(struct super_block *sb, void *data, int silent)
> >   	static struct tree_descr debug_files[] = {{""}};
> >
> >   	return simple_fill_super(sb, DEBUGFS_MAGIC, debug_files,
> > -				 S_IWUSR | S_IRUGO | S_IXUGO);
> > +				 S_IRWXU);
> >   }
> >
> >   static struct dentry *debug_mount(struct file_system_type *fs_type,
> > --
> > 1.7.2.3
> >
> > --
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