| Message ID | 1489841889-27601-1-git-send-email-elena.reshetova@intel.com |
|---|---|
| State | Rejected, archived |
| Delegated to: | David Miller |
| Headers | show |
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 <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> [...] > 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(&fp->refcnt, 0); > + refcount_set(&fp->refcnt, 1); > > if (!sk_filter_charge(sk, fp)) { > kfree(fp); > return -ENOMEM; > } > + refcount_set(&fp->refcnt, 1); Why do it twice? [...] MBR, Sergei
> 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 <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> > [...] > > 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(&fp->refcnt, 0); > > + refcount_set(&fp->refcnt, 1); > > > > if (!sk_filter_charge(sk, fp)) { > > kfree(fp); > > return -ENOMEM; > > } > > + refcount_set(&fp->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.
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); old_fp = rcu_dereference_protected(sk->sk_filter, lockdep_sock_is_held(sk));