[0/3] HID: debug: fix the ring buffer implementation

Message

Vladis Dronov Oct. 3, 2018, 5:19 p.m. UTC

This patchset is fixing some aspects of the ring buffer implementation in
drivers/hid/hid-debug.c. This implementation has certain problem points:

- it may stuck in an infinite loop
- it may return corrupted data
- a reader and a writer are not protected by spinlocks, which can lead to
  the corrupted data

The suggested patchset is a new ring buffer implementation which overwrites
the oldest data in case of an overflow. One can verify the suggested ring
buffer implementation by fuzzing it with modified kernel and fuzzer-reader
at: https://gist.github.com/nefigtut/33d56e3870b67493cc867344aed2a062

Vladis Dronov (3):
  HID: debug: avoid infinite loop and corrupting data
  HID: debug: provide reader-writer locking for the ring buffer
  HID: debug: fix ring buffer implementation

 drivers/hid/hid-debug.c   | 201 ++++++++++++++++++++++++++------------
 include/linux/hid-debug.h |   1 +
 2 files changed, 142 insertions(+), 60 deletions(-)

Comments

Jiri Kosina Oct. 26, 2018, 3:25 p.m. UTC | #1

On Wed, 3 Oct 2018, Vladis Dronov wrote:

> This patchset is fixing some aspects of the ring buffer implementation in
> drivers/hid/hid-debug.c. This implementation has certain problem points:
> 
> - it may stuck in an infinite loop
> - it may return corrupted data
> - a reader and a writer are not protected by spinlocks, which can lead to
>   the corrupted data
> 
> The suggested patchset is a new ring buffer implementation which overwrites
> the oldest data in case of an overflow. One can verify the suggested ring
> buffer implementation by fuzzing it with modified kernel and fuzzer-reader
> at: https://gist.github.com/nefigtut/33d56e3870b67493cc867344aed2a062

Vladis,

thanks for cleaning it up. I actually like your rewrite quite a lot.

Quick question -- how well was it tested in which scenarios?

Vladis Dronov Oct. 29, 2018, 8:51 p.m. UTC | #2

Hello, Jiri,

Thank you for the reply and your opinion. It appeared that my own implementation
of a ring buffer was kind of "inventing a wheel", as "kfifo" is already is the
kernel and it may work as a ring buffer quite well. I would like to rewrite my
patchset and use kfifo instead in a new one. Please, ignore this my patchset and
I'll try to submit v2 soon.

This also will answer to "how was it tested" concern, as I believe, kfifo was
quite tested.

Best regards,
Vladis Dronov | Red Hat, Inc. | Product Security Engineer

----- Original Message -----
> From: "Jiri Kosina" <[e-mail]>
> To: "Vladis Dronov" <[e-mail]>
> Cc: "Benjamin Tissoires" <[e-mail]>, [e-mail], [e-mail]
> Sent: Friday, October 26, 2018 5:25:21 PM
> Subject: Re: [PATCH 0/3] HID: debug: fix the ring buffer implementation
> 
> On Wed, 3 Oct 2018, Vladis Dronov wrote:
> 
> > This patchset is fixing some aspects of the ring buffer implementation in
> > drivers/hid/hid-debug.c. This implementation has certain problem points:
> > 
> > - it may stuck in an infinite loop
> > - it may return corrupted data
> > - a reader and a writer are not protected by spinlocks, which can lead to
> >   the corrupted data
> > 
> > The suggested patchset is a new ring buffer implementation which overwrites
> > the oldest data in case of an overflow. One can verify the suggested ring
> > buffer implementation by fuzzing it with modified kernel and fuzzer-reader
> > at: https://gist.github.com/nefigtut/33d56e3870b67493cc867344aed2a062
> 
> Vladis,
> 
> thanks for cleaning it up. I actually like your rewrite quite a lot.
> 
> Quick question -- how well was it tested in which scenarios?
> 
> --
> Jiri Kosina
> SUSE Labs