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Date: Fri, 01 Jul 2022 13:30:31 -0700 From: John Fastabend <john.fastabend@...il.com> To: John Fastabend <john.fastabend@...il.com>, Liu Jian <liujian56@...wei.com>, john.fastabend@...il.com, jakub@...udflare.com, davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, ast@...nel.org, daniel@...earbox.net, andrii@...nel.org, kafai@...com, songliubraving@...com, yhs@...com, kpsingh@...nel.org, netdev@...r.kernel.org, bpf@...r.kernel.org Cc: liujian56@...wei.com Subject: RE: [PATCH bpf] skmsg: Fix invalid last sg check in sk_msg_recvmsg() John Fastabend wrote: > Liu Jian wrote: > > In sk_psock_skb_ingress_enqueue function, if the linear area + nr_frags + > > frag_list of the SKB has NR_MSG_FRAG_IDS blocks in total, skb_to_sgvec > > will return NR_MSG_FRAG_IDS, then msg->sg.end will be set to > > NR_MSG_FRAG_IDS, and in addition, (NR_MSG_FRAG_IDS - 1) is set to the last > > SG of msg. Recv the msg in sk_msg_recvmsg, when i is (NR_MSG_FRAG_IDS - 1), > > the sk_msg_iter_var_next(i) will change i to 0 (not NR_MSG_FRAG_IDS), the > > judgment condition "msg_rx->sg.start==msg_rx->sg.end" and > > "i != msg_rx->sg.end" can not work. > > > > As a result, the processed msg cannot be deleted from ingress_msg list. > > But the length of all the sge of the msg has changed to 0. Then the next > > recvmsg syscall will process the msg repeatedly, because the length of sge > > is 0, the -EFAULT error is always returned. > > > > Fixes: 604326b41a6f ("bpf, sockmap: convert to generic sk_msg interface") > > Signed-off-by: Liu Jian <liujian56@...wei.com> > > --- > > net/core/skmsg.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/net/core/skmsg.c b/net/core/skmsg.c > > index b0fcd0200e84..a8dbea559c7f 100644 > > --- a/net/core/skmsg.c > > +++ b/net/core/skmsg.c > > @@ -462,7 +462,7 @@ int sk_msg_recvmsg(struct sock *sk, struct sk_psock *psock, struct msghdr *msg, > > > > if (copied == len) > > break; > > - } while (i != msg_rx->sg.end); > > + } while (!sg_is_last(sge)); > > > > if (unlikely(peek)) { > > msg_rx = sk_psock_next_msg(psock, msg_rx); > > @@ -472,7 +472,7 @@ int sk_msg_recvmsg(struct sock *sk, struct sk_psock *psock, struct msghdr *msg, > > } > > > > msg_rx->sg.start = i; > > - if (!sge->length && msg_rx->sg.start == msg_rx->sg.end) { > > + if (!sge->length && sg_is_last(sge)) { > > msg_rx = sk_psock_dequeue_msg(psock); > > kfree_sk_msg(msg_rx); > > } > > -- > > 2.17.1 > > > > Looks correct to me, but I'll test it tomorrow and add a reviewed-by and > tested-by then. Thanks! Still testing but adding ack. Acked-by: John Fastabend <john.fastabend@...il.com>
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