On Sat, Dec 01, 2018 at 01:36:59AM +0800, Xin Long wrote: > In sctp_hash_transport/sctp_epaddr_lookup_transport, it dereferences > a transport's asoc under rcu_read_lock while asoc is freed not after > a grace period, which leads to a use-after-free panic. > > This patch fixes it by calling kfree_rcu to make asoc be freed after > a grace period. > > Note that only the asoc's memory is delayed to free in the patch, it > won't cause sk to linger longer. > > Thanks Neil and Marcelo to make this clear. > Thank you for taking the extra time on this Acked-by: Neil Horman <nhorman@xxxxxxxxxxxxx> > Fixes: 7fda702f9315 ("sctp: use new rhlist interface on sctp transport rhashtable") > Fixes: cd2b70875058 ("sctp: check duplicate node before inserting a new transport") > Reported-by: syzbot+0b05d8aa7cb185107483@xxxxxxxxxxxxxxxxxxxxxxxxx > Reported-by: syzbot+aad231d51b1923158444@xxxxxxxxxxxxxxxxxxxxxxxxx > Suggested-by: Neil Horman <nhorman@xxxxxxxxxxxxx> > Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx> > --- > include/net/sctp/structs.h | 2 ++ > net/sctp/associola.c | 2 +- > 2 files changed, 3 insertions(+), 1 deletion(-) > > diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h > index a11f937..feada35 100644 > --- a/include/net/sctp/structs.h > +++ b/include/net/sctp/structs.h > @@ -2075,6 +2075,8 @@ struct sctp_association { > > __u64 abandoned_unsent[SCTP_PR_INDEX(MAX) + 1]; > __u64 abandoned_sent[SCTP_PR_INDEX(MAX) + 1]; > + > + struct rcu_head rcu; > }; > > > diff --git a/net/sctp/associola.c b/net/sctp/associola.c > index 6a28b96..3702f48 100644 > --- a/net/sctp/associola.c > +++ b/net/sctp/associola.c > @@ -434,7 +434,7 @@ static void sctp_association_destroy(struct sctp_association *asoc) > > WARN_ON(atomic_read(&asoc->rmem_alloc)); > > - kfree(asoc); > + kfree_rcu(asoc, rcu); > SCTP_DBG_OBJCNT_DEC(assoc); > } > > -- > 2.1.0 > >