Re: [vs] DLM debugfs information disclosure via non-null-terminated resource name

[Greg KH <gregkh@linuxfoundation.org>]

On Wed, Mar 11, 2026 at 10:31:22AM +0900, can-yildirim@ymail.ne.jp wrote:
> Dear maintainers,
> There is an possible information disclosure vulnerability in the DLM
> subsystem's debugfs interface.

debugfs is, by default, only readable by root, and contains loads of
stuff like this, as it's full of debug information on the system.  So
much so that many systems do not enable it in their kernels, and others
do not mount it at all.  So it's not really a problem overall from a
security point of view.

> The issue resides in the function
> print_format2_lock() in fs/dlm/debug_fs.c. When a resource name
> is exactly DLM_RESNAME_MAXLEN bytes long and contains no null
> byte, the %s format specifier in a seq_printf call reads beyond
> the intended buffer, exposing adjacent kernel memory.

That's not good, can you just send a patch for this to the developers
and mailing list and they can apply it like normal?

thanks,

greg k-h