Re: [PATCH 6.6] ceph: give up on paths longer than PATH_MAX

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Tue, Jan 07, 2025 at 04:50:08PM +0100, Ilya Dryomov wrote:
> From: Max Kellermann <max.kellermann@ionos.com>
> 
> commit 550f7ca98ee028a606aa75705a7e77b1bd11720f upstream.
> 
> If the full path to be built by ceph_mdsc_build_path() happens to be
> longer than PATH_MAX, then this function will enter an endless (retry)
> loop, effectively blocking the whole task.  Most of the machine
> becomes unusable, making this a very simple and effective DoS
> vulnerability.
> 
> I cannot imagine why this retry was ever implemented, but it seems
> rather useless and harmful to me.  Let's remove it and fail with
> ENAMETOOLONG instead.
> 
> Cc: stable@vger.kernel.org
> Reported-by: Dario Weißer <dario@cure53.de>
> Signed-off-by: Max Kellermann <max.kellermann@ionos.com>
> Reviewed-by: Alex Markuze <amarkuze@redhat.com>
> Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
> [idryomov@gmail.com: backport to 6.6: pr_warn() is still in use]
> ---
>  fs/ceph/mds_client.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)

Thank you, I've dropped the "large" ceph patches from 6.6.y now and
added this one instead.

greg k-h