From: Daniel Borkmann <daniel@iogearbox•net>
To: Elena Reshetova <elena.reshetova@intel•com>, netdev@vger•kernel.org
Cc: bridge@lists•linux-foundation.org, linux-kernel@vger•kernel.org,
kuznet@ms2•inr.ac.ru, jmorris@namei•org, kaber@trash•net,
stephen@networkplumber•org, peterz@infradead•org,
keescook@chromium•org, Hans Liljestrand <ishkamiel@gmail•com>,
David Windsor <dwindsor@gmail•com>,
alexei.starovoitov@gmail•com
Subject: Re: [PATCH 08/17] net: convert sk_filter.refcnt from atomic_t to refcount_t
Date: Thu, 16 Mar 2017 17:04:49 +0100 [thread overview]
Message-ID: <58CAB7A1.8060500@iogearbox.net> (raw)
In-Reply-To: <1489678147-21404-9-git-send-email-elena.reshetova@intel.com>
On 03/16/2017 04:28 PM, Elena Reshetova 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@intel•com>
> Signed-off-by: Hans Liljestrand <ishkamiel@gmail•com>
> Signed-off-by: Kees Cook <keescook@chromium•org>
> Signed-off-by: David Windsor <dwindsor@gmail•com>
> ---
> include/linux/filter.h | 3 ++-
> net/core/filter.c | 7 ++++---
> 2 files changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/filter.h b/include/linux/filter.h
> index 8053c38..20247e7 100644
> --- a/include/linux/filter.h
> +++ b/include/linux/filter.h
> @@ -7,6 +7,7 @@
> #include <stdarg.h>
>
> #include <linux/atomic.h>
> +#include <linux/refcount.h>
> #include <linux/compat.h>
> #include <linux/skbuff.h>
> #include <linux/linkage.h>
> @@ -431,7 +432,7 @@ struct bpf_prog {
> };
>
> struct sk_filter {
> - atomic_t refcnt;
> + refcount_t refcnt;
> struct rcu_head rcu;
> struct bpf_prog *prog;
> };
> diff --git a/net/core/filter.c b/net/core/filter.c
> index ebaeaf2..62267e2 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -928,7 +928,7 @@ static void sk_filter_release_rcu(struct rcu_head *rcu)
> */
> static void sk_filter_release(struct sk_filter *fp)
> {
> - if (atomic_dec_and_test(&fp->refcnt))
> + if (refcount_dec_and_test(&fp->refcnt))
> call_rcu(&fp->rcu, sk_filter_release_rcu);
> }
>
> @@ -950,7 +950,7 @@ bool sk_filter_charge(struct sock *sk, struct sk_filter *fp)
> /* same check as in sock_kmalloc() */
> if (filter_size <= sysctl_optmem_max &&
> atomic_read(&sk->sk_omem_alloc) + filter_size < sysctl_optmem_max) {
> - atomic_inc(&fp->refcnt);
> + refcount_inc(&fp->refcnt);
> atomic_add(filter_size, &sk->sk_omem_alloc);
> return true;
> }
> @@ -1179,12 +1179,13 @@ static int __sk_attach_prog(struct bpf_prog *prog, struct sock *sk)
> return -ENOMEM;
>
> fp->prog = prog;
> - atomic_set(&fp->refcnt, 0);
> + refcount_set(&fp->refcnt, 1);
>
> if (!sk_filter_charge(sk, fp)) {
> kfree(fp);
> return -ENOMEM;
> }
> + refcount_set(&fp->refcnt, 1);
Regarding the two subsequent refcount_set(, 1) that look a bit strange
due to the sk_filter_charge() having refcount_inc() I presume ... can't
the refcount API handle such corner case? Or alternatively the let the
sk_filter_charge() handle it, for example:
bool __sk_filter_charge(struct sock *sk, struct sk_filter *fp)
{
u32 filter_size = bpf_prog_size(fp->prog->len);
/* same check as in sock_kmalloc() */
if (filter_size <= sysctl_optmem_max &&
atomic_read(&sk->sk_omem_alloc) + filter_size < sysctl_optmem_max) {
atomic_add(filter_size, &sk->sk_omem_alloc);
return true;
}
return false;
}
And this goes to filter.h:
bool __sk_filter_charge(struct sock *sk, struct sk_filter *fp);
bool sk_filter_charge(struct sock *sk, struct sk_filter *fp)
{
bool ret = __sk_filter_charge(sk, fp);
if (ret)
refcount_inc(&fp->refcnt);
return ret;
}
... and let __sk_attach_prog() call __sk_filter_charge() and only fo
the second refcount_set()?
> old_fp = rcu_dereference_protected(sk->sk_filter,
> lockdep_sock_is_held(sk));
>
next prev parent reply other threads:[~2017-03-16 16:04 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-16 15:28 [PATCH 00/17] net subsystem refcount conversions Elena Reshetova
2017-03-16 15:28 ` [PATCH 01/17] net: convert neighbour.refcnt from atomic_t to refcount_t Elena Reshetova
2017-03-16 15:28 ` [PATCH 02/17] net: convert neigh_params.refcnt " Elena Reshetova
2017-03-16 15:28 ` [PATCH 03/17] net: convert nf_bridge_info.use " Elena Reshetova
2017-03-16 15:28 ` [PATCH 04/17] net: convert sk_buff.users " Elena Reshetova
2017-03-16 15:28 ` [PATCH 05/17] net: convert sk_buff_fclones.fclone_ref " Elena Reshetova
2017-03-16 15:28 ` [PATCH 06/17] net: convert sock.sk_wmem_alloc " Elena Reshetova
2017-03-16 15:28 ` [PATCH 07/17] net: convert sock.sk_refcnt " Elena Reshetova
2017-03-16 16:58 ` Eric Dumazet
2017-03-16 17:38 ` Kees Cook
2017-03-16 19:10 ` David Miller
2017-03-17 7:42 ` Reshetova, Elena
2017-03-17 16:13 ` Eric Dumazet
2017-03-18 16:47 ` Herbert Xu
2017-03-19 1:21 ` David Miller
2017-03-20 10:39 ` Peter Zijlstra
2017-03-20 13:16 ` Herbert Xu
2017-03-20 13:23 ` Peter Zijlstra
2017-03-20 13:27 ` Herbert Xu
2017-03-20 13:40 ` Peter Zijlstra
2017-03-20 14:51 ` Eric Dumazet
2017-03-20 14:59 ` Eric Dumazet
2017-03-20 16:18 ` Eric Dumazet
2017-03-20 16:34 ` Eric Dumazet
2017-03-20 14:59 ` Peter Zijlstra
2017-03-21 20:49 ` Kees Cook
2017-03-21 21:23 ` Eric Dumazet
2017-03-21 22:36 ` David Miller
2017-03-21 23:51 ` Kees Cook
2017-03-22 2:03 ` Eric Dumazet
2017-03-22 12:25 ` Peter Zijlstra
2017-03-22 13:22 ` Eric Dumazet
2017-03-22 14:33 ` Peter Zijlstra
2017-03-22 14:54 ` Eric Dumazet
2017-03-22 15:08 ` Peter Zijlstra
2017-03-22 15:22 ` Eric Dumazet
2017-03-22 16:51 ` Peter Zijlstra
2017-03-22 19:08 ` Kees Cook
2017-03-22 12:11 ` Peter Zijlstra
2017-03-20 14:10 ` David Laight
2017-03-20 14:28 ` Peter Zijlstra
2017-03-20 15:00 ` David Laight
2017-03-16 15:28 ` [PATCH 08/17] net: convert sk_filter.refcnt " Elena Reshetova
2017-03-16 16:04 ` Daniel Borkmann [this message]
2017-03-17 8:02 ` Reshetova, Elena
2017-03-16 15:28 ` [PATCH 09/17] net: convert ip_mc_list.refcnt " Elena Reshetova
2017-03-16 15:29 ` [PATCH 10/17] net: convert in_device.refcnt " Elena Reshetova
2017-03-16 15:29 ` [PATCH 11/17] net: convert netpoll_info.refcnt " Elena Reshetova
2017-03-16 15:29 ` [PATCH 12/17] net: convert unix_address.refcnt " Elena Reshetova
2017-03-16 15:29 ` [PATCH 13/17] net: convert fib_rule.refcnt " Elena Reshetova
2017-03-16 15:29 ` [PATCH 14/17] net: convert inet_frag_queue.refcnt " Elena Reshetova
2017-03-16 15:29 ` [PATCH 15/17] net: convert net.passive " Elena Reshetova
2017-03-16 15:29 ` [PATCH 16/17] net: convert netlbl_lsm_cache.refcount " Elena Reshetova
2017-03-16 15:29 ` [PATCH 17/17] net: convert packet_fanout.sk_ref " Elena Reshetova
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