RE: [PATCH] net: convert sk_filter.refcnt from atomic_t to refcount_t

[Reshetova, Elena]

> 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(>refcnt))
> > +   if (refcount_dec_and_test(>refcnt))
> > call_rcu(>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_omem_alloc) + filter_size <
> sysctl_optmem_max) {
> > -   atomic_inc(>refcnt);
> > atomic_add(filter_size, >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 
> 
> 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

Re: [PATCH] net: convert sk_filter.refcnt from atomic_t to refcount_t

[Daniel Borkmann]

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(>refcnt))
+   if (refcount_dec_and_test(>refcnt))
call_rcu(>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_omem_alloc) + filter_size < sysctl_optmem_max) {
-   atomic_inc(>refcnt);
atomic_add(filter_size, >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 

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

RE: [PATCH] net: convert sk_filter.refcnt from atomic_t to refcount_t

[Reshetova, Elena]

> Hello!
> 
> On 3/18/2017 3:58 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 
> > Signed-off-by: Hans Liljestrand 
> > Signed-off-by: Kees Cook 
> > Signed-off-by: David Windsor 
> [...]
> > 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
> [...]
> > @@ -1179,12 +1179,13 @@ static int __sk_attach_prog(struct bpf_prog *prog,
> struct sock *sk)
> > return -ENOMEM;
> >
> > fp->prog = prog;
> > -   atomic_set(>refcnt, 0);
> > +   refcount_set(>refcnt, 1);
> >
> > if (!sk_filter_charge(sk, fp)) {
> > kfree(fp);
> > return -ENOMEM;
> > }
> > +   refcount_set(>refcnt, 1);
> 
> Why do it twice?
> 
> [...]
> 
> MBR, Sergei

Sorry I just realized that I had unsquashed changes when I sent this patch, so 
this is still the old version. 
Will send a new one now. 

Best Regards,
Elena.

[PATCH] net: convert sk_filter.refcnt from atomic_t to refcount_t

[Elena Reshetova]

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 
Signed-off-by: Hans Liljestrand 
Signed-off-by: Kees Cook 
Signed-off-by: David Windsor 
---
 include/linux/filter.h |  3 ++-
 net/core/filter.c  | 17 -
 2 files changed, 14 insertions(+), 6 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 
 
 #include 
+#include 
 #include 
 #include 
 #include 
@@ -431,7 +432,7 @@ struct bpf_prog {
 };
 
 struct sk_filter {
-   atomic_trefcnt;
+   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(>refcnt))
+   if (refcount_dec_and_test(>refcnt))
call_rcu(>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_omem_alloc) + filter_size < sysctl_optmem_max) {
-   atomic_inc(>refcnt);
atomic_add(filter_size, >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(>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(>refcnt, 0);
 
-   if (!sk_filter_charge(sk, fp)) {
+   if (!__sk_filter_charge(sk, fp)) {
kfree(fp);
return -ENOMEM;
}
+   refcount_set(>refcnt, 1);
 
old_fp = rcu_dereference_protected(sk->sk_filter,
   lockdep_sock_is_held(sk));
-- 
2.7.4

Re: [PATCH] net: convert sk_filter.refcnt from atomic_t to refcount_t

[Sergei Shtylyov]

Hello!

On 3/18/2017 3:58 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 
Signed-off-by: Hans Liljestrand 
Signed-off-by: Kees Cook 
Signed-off-by: David Windsor 

[...]

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

[...]

@@ -1179,12 +1179,13 @@ static int __sk_attach_prog(struct bpf_prog *prog, 
struct sock *sk)
return -ENOMEM;

fp->prog = prog;
-   atomic_set(>refcnt, 0);
+   refcount_set(>refcnt, 1);

if (!sk_filter_charge(sk, fp)) {
kfree(fp);
return -ENOMEM;
}
+   refcount_set(>refcnt, 1);


   Why do it twice?

[...]

MBR, Sergei

[PATCH] net: convert sk_filter.refcnt from atomic_t to refcount_t

[Elena Reshetova]

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 
Signed-off-by: Hans Liljestrand 
Signed-off-by: Kees Cook 
Signed-off-by: David Windsor 
---
 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 
 
 #include 
+#include 
 #include 
 #include 
 #include 
@@ -431,7 +432,7 @@ struct bpf_prog {
 };
 
 struct sk_filter {
-   atomic_trefcnt;
+   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(>refcnt))
+   if (refcount_dec_and_test(>refcnt))
call_rcu(>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_omem_alloc) + filter_size < sysctl_optmem_max) {
-   atomic_inc(>refcnt);
+   refcount_inc(>refcnt);
atomic_add(filter_size, >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(>refcnt, 0);
+   refcount_set(>refcnt, 1);
 
if (!sk_filter_charge(sk, fp)) {
kfree(fp);
return -ENOMEM;
}
+   refcount_set(>refcnt, 1);
 
old_fp = rcu_dereference_protected(sk->sk_filter,
   lockdep_sock_is_held(sk));
-- 
2.7.4