On Wed, 12 Nov 2014 18:04:04 -0500
Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx> wrote:
> Both xprt_lookup_rqst() and xprt_complete_rqst() require that you
> take the transport lock in order to avoid races with xprt_transmit().
>
> Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
> Cc: Bruce Fields <bfields@xxxxxxxxxxxx>
> ---
> net/sunrpc/svcsock.c | 27 ++++++++++++++++-----------
> 1 file changed, 16 insertions(+), 11 deletions(-)
>
> diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
> index 3f959c681885..f9c052d508f0 100644
> --- a/net/sunrpc/svcsock.c
> +++ b/net/sunrpc/svcsock.c
> @@ -1019,17 +1019,12 @@ static int receive_cb_reply(struct svc_sock *svsk, struct svc_rqst *rqstp)
> xid = *p++;
> calldir = *p;
>
> - if (bc_xprt)
> - req = xprt_lookup_rqst(bc_xprt, xid);
> -
> - if (!req) {
> - printk(KERN_NOTICE
> - "%s: Got unrecognized reply: "
> - "calldir 0x%x xpt_bc_xprt %p xid %08x\n",
> - __func__, ntohl(calldir),
> - bc_xprt, ntohl(xid));
> + if (!bc_xprt)
> return -EAGAIN;
> - }
> + spin_lock_bh(&bc_xprt->transport_lock);
> + req = xprt_lookup_rqst(bc_xprt, xid);
> + if (!req)
> + goto unlock_notfound;
>
> memcpy(&req->rq_private_buf, &req->rq_rcv_buf, sizeof(struct xdr_buf));
> /*
> @@ -1040,11 +1035,21 @@ static int receive_cb_reply(struct svc_sock *svsk, struct svc_rqst *rqstp)
> dst = &req->rq_private_buf.head[0];
> src = &rqstp->rq_arg.head[0];
> if (dst->iov_len < src->iov_len)
> - return -EAGAIN; /* whatever; just giving up. */
> + goto unlock_eagain; /* whatever; just giving up. */
> memcpy(dst->iov_base, src->iov_base, src->iov_len);
> xprt_complete_rqst(req->rq_task, rqstp->rq_arg.len);
> rqstp->rq_arg.len = 0;
> + spin_unlock_bh(&bc_xprt->transport_lock);
> return 0;
> +unlock_notfound:
> + printk(KERN_NOTICE
> + "%s: Got unrecognized reply: "
> + "calldir 0x%x xpt_bc_xprt %p xid %08x\n",
> + __func__, ntohl(calldir),
> + bc_xprt, ntohl(xid));
> +unlock_eagain:
> + spin_unlock_bh(&bc_xprt->transport_lock);
> + return -EAGAIN;
> }
>
> static int copy_pages_to_kvecs(struct kvec *vec, struct page **pages, int len)
Nice catch. It would also be good to pair this with a
lockdep_assert_held() call in xprt_lookup_rqst, but that could be added
in a separate patch.
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
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