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

David Daney
2011-02-22T18:32:32Z

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@canonical.com>
>> ---
>> 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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