Re: [PATCH] sctp: fix refcount bug in sctp_wfree
From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Date: 2020-03-17 04:15:48
Also in:
linux-sctp, lkml
On Mon, Mar 16, 2020 at 11:53:24AM +0800, Qiujun Huang wrote:
Do accounting for skb's real sk. In some case skb->sk != asoc->base.sk.
This is a too simple description. Please elaborate how this can
happen in sctp_wfree. Especially considering the construct for
migrating the tx queue on sctp_sock_migrate(), as both sockets are
locked while moving the chunks around and the asoc itself is only
moved in between decrementing and incrementing the refcount:
lock_sock_nested(newsk, SINGLE_DEPTH_NESTING);
sctp_for_each_tx_datachunk(assoc, sctp_clear_owner_w);
sctp_assoc_migrate(assoc, newsk);
sctp_for_each_tx_datachunk(assoc, sctp_set_owner_w);
...
Reported-and-tested-by: syzbot+cea71eec5d6de256d54d@syzkaller.appspotmail.com
I can't see a positive test result, though. If I didn't loose any email, your last test with a patch similar to this one actually failed. I'm talking about syzbot test result at Message-ID: [ref]
quoted hunk ↗ jump to hunk
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 1b56fc4..5f5c28b 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); }-- 1.8.3.1