xprtrdma: Fix use-after-free in rpcrdma_post_recvs

Dereference wr->next /before/ the memory backing wr has been
released. This issue was found by code inspection. It is not
expected to be a significant problem because it is in an error
path that is almost never executed.

Fixes: 7c8d9e7c8863 ("xprtrdma: Move Receive posting to ... ")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index 84bb379..e71315e 100644 (file)
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -1553,10 +1553,11 @@ rpcrdma_post_recvs(struct rpcrdma_xprt *r_xprt, bool temp)
        rc = ib_post_recv(r_xprt->rx_ia.ri_id->qp, wr,
                          (const struct ib_recv_wr **)&bad_wr);
        if (rc) {
-               for (wr = bad_wr; wr; wr = wr->next) {
+               for (wr = bad_wr; wr;) {
                        struct rpcrdma_rep *rep;
 
                        rep = container_of(wr, struct rpcrdma_rep, rr_recv_wr);
+                       wr = wr->next;
                        rpcrdma_recv_buffer_put(rep);
                        --count;
                }