linux-kernel - Re: [PATCH 05/23] net, ceph: convert ceph_osd.o_ref from atomic_t to refcount

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Date:   Fri, 24 Mar 2017 14:49:24 +0100
From:   Ilya Dryomov <idryomov@...il.com>
To:     Elena Reshetova <elena.reshetova@...el.com>
Cc:     netdev <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-rdma@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>, linux-x25@...r.kernel.org,
        linux-sctp@...r.kernel.org, vyasevich@...il.com,
        nhorman@...driver.com, linux-hams@...r.kernel.org,
        linux-nfs@...r.kernel.org,
        Ceph Development <ceph-devel@...r.kernel.org>,
        "Yan, Zheng" <zyan@...hat.com>, Sage Weil <sage@...hat.com>,
        bfields@...ldses.org, Jeff Layton <jlayton@...chiereds.net>,
        steffen.klassert@...unet.com,
        Herbert Xu <herbert@...dor.apana.org.au>,
        santosh.shilimkar@...cle.com, jreuter@...na.de,
        ralf@...ux-mips.org, peterz@...radead.org,
        Kees Cook <keescook@...omium.org>,
        Hans Liljestrand <ishkamiel@...il.com>,
        David Windsor <dwindsor@...il.com>
Subject: Re: [PATCH 05/23] net, ceph: convert ceph_osd.o_ref from atomic_t to refcount_t

On Fri, Mar 17, 2017 at 1:10 PM, Elena Reshetova
<elena.reshetova@...el.com> wrote:
> refcount_t type and corresponding API should be
> used instead of atomic_t when the variable is used as
> a reference counter. This allows to avoid accidental
> refcounter overflows that might lead to use-after-free
> situations.
>
> Signed-off-by: Elena Reshetova <elena.reshetova@...el.com>
> Signed-off-by: Hans Liljestrand <ishkamiel@...il.com>
> Signed-off-by: Kees Cook <keescook@...omium.org>
> Signed-off-by: David Windsor <dwindsor@...il.com>
> ---
>  include/linux/ceph/osd_client.h |  3 ++-
>  net/ceph/osd_client.c           | 16 ++++++++--------
>  2 files changed, 10 insertions(+), 9 deletions(-)
>
> diff --git a/include/linux/ceph/osd_client.h b/include/linux/ceph/osd_client.h
> index 2ea0c28..5ce0cd6 100644
> --- a/include/linux/ceph/osd_client.h
> +++ b/include/linux/ceph/osd_client.h
> @@ -5,6 +5,7 @@
>  #include <linux/kref.h>
>  #include <linux/mempool.h>
>  #include <linux/rbtree.h>
> +#include <linux/refcount.h>
>
>  #include <linux/ceph/types.h>
>  #include <linux/ceph/osdmap.h>
> @@ -27,7 +28,7 @@ typedef void (*ceph_osdc_callback_t)(struct ceph_osd_request *);
>
>  /* a given osd we're communicating with */
>  struct ceph_osd {
> -       atomic_t o_ref;
> +       refcount_t o_ref;
>         struct ceph_osd_client *o_osdc;
>         int o_osd;
>         int o_incarnation;
> diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
> index b65bbf9..99a51f0 100644
> --- a/net/ceph/osd_client.c
> +++ b/net/ceph/osd_client.c
> @@ -1005,7 +1005,7 @@ static bool osd_registered(struct ceph_osd *osd)
>   */
>  static void osd_init(struct ceph_osd *osd)
>  {
> -       atomic_set(&osd->o_ref, 1);
> +       refcount_set(&osd->o_ref, 1);
>         RB_CLEAR_NODE(&osd->o_node);
>         osd->o_requests = RB_ROOT;
>         osd->o_linger_requests = RB_ROOT;
> @@ -1050,9 +1050,9 @@ static struct ceph_osd *create_osd(struct ceph_osd_client *osdc, int onum)
>
>  static struct ceph_osd *get_osd(struct ceph_osd *osd)
>  {
> -       if (atomic_inc_not_zero(&osd->o_ref)) {
> -               dout("get_osd %p %d -> %d\n", osd, atomic_read(&osd->o_ref)-1,
> -                    atomic_read(&osd->o_ref));
> +       if (refcount_inc_not_zero(&osd->o_ref)) {
> +               dout("get_osd %p %d -> %d\n", osd, refcount_read(&osd->o_ref)-1,
> +                    refcount_read(&osd->o_ref));
>                 return osd;
>         } else {
>                 dout("get_osd %p FAIL\n", osd);
> @@ -1062,9 +1062,9 @@ static struct ceph_osd *get_osd(struct ceph_osd *osd)
>
>  static void put_osd(struct ceph_osd *osd)
>  {
> -       dout("put_osd %p %d -> %d\n", osd, atomic_read(&osd->o_ref),
> -            atomic_read(&osd->o_ref) - 1);
> -       if (atomic_dec_and_test(&osd->o_ref)) {
> +       dout("put_osd %p %d -> %d\n", osd, refcount_read(&osd->o_ref),
> +            refcount_read(&osd->o_ref) - 1);
> +       if (refcount_dec_and_test(&osd->o_ref)) {
>                 osd_cleanup(osd);
>                 kfree(osd);
>         }
> @@ -4092,7 +4092,7 @@ void ceph_osdc_stop(struct ceph_osd_client *osdc)
>                 close_osd(osd);
>         }
>         up_write(&osdc->lock);
> -       WARN_ON(atomic_read(&osdc->homeless_osd.o_ref) != 1);
> +       WARN_ON(refcount_read(&osdc->homeless_osd.o_ref) != 1);
>         osd_cleanup(&osdc->homeless_osd);
>
>         WARN_ON(!list_empty(&osdc->osd_lru));

Applied.

Thanks,

                Ilya