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Commit 4c355cdf authored by Reshetova, Elena's avatar Reshetova, Elena Committed by David S. Miller
Browse files

net: convert sk_filter.refcnt from atomic_t to refcount_t 



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: default avatarElena Reshetova <elena.reshetova@intel.com>
Signed-off-by: default avatarHans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarDavid Windsor <dwindsor@gmail.com>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 726bceca

include/linux/filter.h

+2 −1
Original line number Diff line number Diff line
@@ -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>
@@ -430,7 +431,7 @@ struct bpf_prog { 
};



struct sk_filter {

	atomic_t	refcnt;

	refcount_t	refcnt;

	struct rcu_head	rcu;

	struct bpf_prog	*prog;

};

net/core/filter.c

+12 −5
Original line number Diff line number Diff line
@@ -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)

static 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));