On Wed, Mar 22, 2017 at 10:15:02AM +0800, gfree.wind@xxxxxxxxxxx wrote:
> From: Gao Feng <fgao@xxxxxxxxxx>
>
> Because these two functions return the nf_ct_helper_expectfn pointer
> which should be protected by rcu lock. So it should makes sure the
> caller should hold the rcu lock, not inside these functions.
>
> Signed-off-by: Gao Feng <fgao@xxxxxxxxxx>
> ---
> v2: Shorter subject, per Pablo
> v1: Initial version
>
> net/netfilter/nf_conntrack_helper.c | 6 ++----
> 1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/net/netfilter/nf_conntrack_helper.c b/net/netfilter/nf_conntrack_helper.c
> index 6dc44d9..bce3d1f 100644
> --- a/net/netfilter/nf_conntrack_helper.c
> +++ b/net/netfilter/nf_conntrack_helper.c
> @@ -311,38 +311,36 @@ void nf_ct_helper_expectfn_unregister(struct nf_ct_helper_expectfn *n)
> }
> EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_unregister);
>
> +/* Caller should hold the rcu lock */
> struct nf_ct_helper_expectfn *
> nf_ct_helper_expectfn_find_by_name(const char *name)
> {
> struct nf_ct_helper_expectfn *cur;
> bool found = false;
>
> - rcu_read_lock();
> list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
> if (!strcmp(cur->name, name)) {
> found = true;
> break;
> }
> }
> - rcu_read_unlock();
> return found ? cur : NULL;
> }
> EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_name);
nf_ct_helper_expectfn_find_by_name() is called from ctnetlink, via
ctnetlink_create_expect() and rcu read side lock is not held there.
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