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: 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> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -7,6 +7,7 @@
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#include <stdarg.h>
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#include <linux/atomic.h>
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#include <linux/refcount.h>
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#include <linux/compat.h>
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#include <linux/skbuff.h>
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#include <linux/linkage.h>
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@ -430,7 +431,7 @@ struct bpf_prog {
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};
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struct sk_filter {
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atomic_t refcnt;
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refcount_t refcnt;
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struct rcu_head rcu;
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struct bpf_prog *prog;
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};
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@ -928,7 +928,7 @@ static void sk_filter_release_rcu(struct rcu_head *rcu)
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*/
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static void sk_filter_release(struct sk_filter *fp)
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{
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if (atomic_dec_and_test(&fp->refcnt))
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if (refcount_dec_and_test(&fp->refcnt))
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call_rcu(&fp->rcu, sk_filter_release_rcu);
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}
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@ -943,20 +943,27 @@ void sk_filter_uncharge(struct sock *sk, struct sk_filter *fp)
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/* try to charge the socket memory if there is space available
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* return true on success
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*/
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bool sk_filter_charge(struct sock *sk, struct sk_filter *fp)
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static bool __sk_filter_charge(struct sock *sk, struct sk_filter *fp)
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{
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u32 filter_size = bpf_prog_size(fp->prog->len);
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/* same check as in sock_kmalloc() */
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if (filter_size <= sysctl_optmem_max &&
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atomic_read(&sk->sk_omem_alloc) + filter_size < sysctl_optmem_max) {
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atomic_inc(&fp->refcnt);
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atomic_add(filter_size, &sk->sk_omem_alloc);
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return true;
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}
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return false;
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}
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bool sk_filter_charge(struct sock *sk, struct sk_filter *fp)
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{
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bool ret = __sk_filter_charge(sk, fp);
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if (ret)
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refcount_inc(&fp->refcnt);
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return ret;
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}
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static struct bpf_prog *bpf_migrate_filter(struct bpf_prog *fp)
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{
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struct sock_filter *old_prog;
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@ -1179,12 +1186,12 @@ static int __sk_attach_prog(struct bpf_prog *prog, struct sock *sk)
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return -ENOMEM;
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fp->prog = prog;
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atomic_set(&fp->refcnt, 0);
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if (!sk_filter_charge(sk, fp)) {
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if (!__sk_filter_charge(sk, fp)) {
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kfree(fp);
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return -ENOMEM;
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}
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refcount_set(&fp->refcnt, 1);
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old_fp = rcu_dereference_protected(sk->sk_filter,
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lockdep_sock_is_held(sk));
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