net: convert sk_filter.refcnt from atomic_t to refcount_t

Submitted by Reshetova, Elena on March 20, 2017, 9:37 a.m.

Details

Message ID 1490002641-10498-1-git-send-email-elena.reshetova@intel.com
State Rejected
Delegated to: David Miller
Headers show

Commit Message

Reshetova, Elena March 20, 2017, 9:37 a.m.
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      | 17 ++++++++++++-----
 2 files changed, 14 insertions(+), 6 deletions(-)

Comments

Daniel Borkmann March 20, 2017, 5:13 p.m.
On 03/20/2017 10:37 AM, Elena Reshetova wrote:
[...]
> diff --git a/net/core/filter.c b/net/core/filter.c
> index ebaeaf2..389cb8d 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);
>   }
>
> @@ -943,20 +943,27 @@ void sk_filter_uncharge(struct sock *sk, struct sk_filter *fp)
>   /* try to charge the socket memory if there is space available
>    * return true on success
>    */
> -bool sk_filter_charge(struct sock *sk, struct sk_filter *fp)
> +bool __sk_filter_charge(struct sock *sk, struct sk_filter *fp)

And this then becomes: static bool __sk_filter_charge(...)

>   {
>   	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_inc(&fp->refcnt);
>   		atomic_add(filter_size, &sk->sk_omem_alloc);
>   		return true;
>   	}
>   	return false;
>   }

Since here is just all in slow-path, looks fine to me if the above
is addressed as well in v3:

Acked-by: Daniel Borkmann <daniel@iogearbox.net>

Please make sure you add [PATCH net-next] in your subject in future
so that it's clear which tree this goes to.

Thanks,
Daniel
Reshetova, Elena March 21, 2017, 10:43 a.m.
> On 03/20/2017 10:37 AM, Elena Reshetova wrote:
> [...]
> > diff --git a/net/core/filter.c b/net/core/filter.c
> > index ebaeaf2..389cb8d 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);
> >   }
> >
> > @@ -943,20 +943,27 @@ void sk_filter_uncharge(struct sock *sk, struct
> sk_filter *fp)
> >   /* try to charge the socket memory if there is space available
> >    * return true on success
> >    */
> > -bool sk_filter_charge(struct sock *sk, struct sk_filter *fp)
> > +bool __sk_filter_charge(struct sock *sk, struct sk_filter *fp)
> 
> And this then becomes: static bool __sk_filter_charge(...)

Ups, I guess I am getting too tired of all these patch sendings, so more and more mistakes slide in. 
Will try switching to smth else to get attention back in order. 

> 
> >   {
> >   	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_inc(&fp->refcnt);
> >   		atomic_add(filter_size, &sk->sk_omem_alloc);
> >   		return true;
> >   	}
> >   	return false;
> >   }
> 
> Since here is just all in slow-path, looks fine to me if the above
> is addressed as well in v3:
> 
> Acked-by: Daniel Borkmann <daniel@iogearbox.net>
> 
> Please make sure you add [PATCH net-next] in your subject in future
> so that it's clear which tree this goes to.

Thank you very much! Will do. 

Best Regards,
Elena.
> 
> Thanks,
> Daniel

Patch hide | download patch | download mbox

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..389cb8d 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);
 }
 
@@ -943,20 +943,27 @@  void sk_filter_uncharge(struct sock *sk, struct sk_filter *fp)
 /* try to charge the socket memory if there is space available
  * return true on success
  */
-bool sk_filter_charge(struct sock *sk, struct sk_filter *fp)
+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_inc(&fp->refcnt);
 		atomic_add(filter_size, &sk->sk_omem_alloc);
 		return true;
 	}
 	return false;
 }
 
+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;
+}
+
 static struct bpf_prog *bpf_migrate_filter(struct bpf_prog *fp)
 {
 	struct sock_filter *old_prog;
@@ -1179,12 +1186,12 @@  static int __sk_attach_prog(struct bpf_prog *prog, struct sock *sk)
 		return -ENOMEM;
 
 	fp->prog = prog;
-	atomic_set(&fp->refcnt, 0);
 
-	if (!sk_filter_charge(sk, fp)) {
+	if (!__sk_filter_charge(sk, fp)) {
 		kfree(fp);
 		return -ENOMEM;
 	}
+	refcount_set(&fp->refcnt, 1);
 
 	old_fp = rcu_dereference_protected(sk->sk_filter,
 					   lockdep_sock_is_held(sk));