Commit 773f6c5b authored by Chuck Lever's avatar Chuck Lever
Browse files

svcrdma: Prevent a UAF in svc_rdma_send() 



In some error flow cases, svc_rdma_wc_send() releases @ctxt. Copy
the sc_cid field in @ctxt to a stack variable in order to guarantee
that the value is available after the ib_post_send() call.

In case the new comment looks a little strange, this will be done
with at least one more field in a subsequent patch.

Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
parent 5b9a8589

net/sunrpc/xprtrdma/svc_rdma_sendto.c

+8 −3
Original line number Diff line number Diff line
@@ -316,12 +316,17 @@ static void svc_rdma_wc_send(struct ib_cq *cq, struct ib_wc *wc) 
 * @rdma: transport on which to post the WR

 * @ctxt: send ctxt with a Send WR ready to post

 *

 * Copy fields in @ctxt to stack variables in order to guarantee

 * that these values remain available after the ib_post_send() call.

 * In some error flow cases, svc_rdma_wc_send() releases @ctxt.

 *

 * Returns zero if the Send WR was posted successfully. Otherwise, a

 * negative errno is returned.

 */

int svc_rdma_send(struct svcxprt_rdma *rdma, struct svc_rdma_send_ctxt *ctxt)

{

	struct ib_send_wr *wr = &ctxt->sc_send_wr;

	struct rpc_rdma_cid cid = ctxt->sc_cid;

	int ret;



	might_sleep();
@@ -337,12 +342,12 @@ int svc_rdma_send(struct svcxprt_rdma *rdma, struct svc_rdma_send_ctxt *ctxt) 
		if ((atomic_dec_return(&rdma->sc_sq_avail) < 0)) {

			svc_rdma_wake_send_waiters(rdma, 1);

			percpu_counter_inc(&svcrdma_stat_sq_starve);

			trace_svcrdma_sq_full(rdma, &ctxt->sc_cid);

			trace_svcrdma_sq_full(rdma, &cid);

			wait_event(rdma->sc_send_wait,

				   atomic_read(&rdma->sc_sq_avail) > 0);

			if (test_bit(XPT_CLOSE, &rdma->sc_xprt.xpt_flags))

				return -ENOTCONN;

			trace_svcrdma_sq_retry(rdma, &ctxt->sc_cid);

			trace_svcrdma_sq_retry(rdma, &cid);

			continue;

		}
@@ -353,7 +358,7 @@ int svc_rdma_send(struct svcxprt_rdma *rdma, struct svc_rdma_send_ctxt *ctxt) 
		return 0;

	}



	trace_svcrdma_sq_post_err(rdma, &ctxt->sc_cid, ret);

	trace_svcrdma_sq_post_err(rdma, &cid, ret);

	svc_xprt_deferred_close(&rdma->sc_xprt);

	svc_rdma_wake_send_waiters(rdma, 1);

	return ret;