Re: [PATCH v2] sctp: fix refcount bug in sctp_wfree
From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Date: 2020-03-17 17:30:47
Also in:
linux-sctp, lkml
Hi, On Tue, Mar 17, 2020 at 11:55:36PM +0800, Qiujun Huang wrote:
Do accounting for skb's real sk. In some case skb->sk != asoc->base.sk: migrate routing sctp_check_transmitted routing ------------ ---------------
sctp_close();
lock_sock(sk2);
sctp_primitive_ABORT();
sctp_do_sm();
sctp_cmd_interpreter();
sctp_cmd_process_sack();
sctp_outq_sack();
sctp_check_transmitted();
lock_sock(sk1);
sctp_getsockopt_peeloff();
sctp_do_peeloff();
sctp_sock_migrate();lock_sock_nested(sk2);
mv the transmitted skb to
the it's local tlistHow can sctp_do_sm() be called in the 2nd column so that it bypasses the locks in the left column, allowing this mv to happen?
sctp_for_each_tx_datachunk(
sctp_clear_owner_w);
sctp_assoc_migrate();
sctp_for_each_tx_datachunk(
sctp_set_owner_w);
put the skb back to the
assoc lists
----------------------------------------------------
The skbs which held bysctp_check_transmitted were not changed
to newsk. They were not dealt with by sctp_for_each_tx_datachunk
(sctp_clear_owner_w/sctp_set_owner_w).It would make sense but I'm missing one step earlier, I'm not seeing how the move to local list is allowed/possible in there. It really shouldn't be possible.
quoted hunk ↗ jump to hunk
It looks only trouble here so handling it in sctp_wfree is enough. Reported-and-tested-by: syzbot+cea71eec5d6de256d54d@syzkaller.appspotmail.com Signed-off-by: Qiujun Huang <redacted> --- net/sctp/socket.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)diff --git a/net/sctp/socket.c b/net/sctp/socket.c index 1b56fc440606..5f5c28b30e25 100644 --- a/net/sctp/socket.c +++ b/net/sctp/socket.c@@ -9080,7 +9080,7 @@ static void sctp_wfree(struct sk_buff *skb) { struct sctp_chunk *chunk = skb_shinfo(skb)->destructor_arg; struct sctp_association *asoc = chunk->asoc; - struct sock *sk = asoc->base.sk; + struct sock *sk = skb->sk; sk_mem_uncharge(sk, skb->truesize); sk->sk_wmem_queued -= skb->truesize + sizeof(struct sctp_chunk);@@ -9109,7 +9109,7 @@ static void sctp_wfree(struct sk_buff *skb) } sock_wfree(skb); - sctp_wake_up_waiters(sk, asoc); + sctp_wake_up_waiters(asoc->base.sk, asoc); sctp_association_put(asoc); }-- 2.17.1