From 26190394c64c9429481fc88a4738f70bb92fb352 Mon Sep 17 00:00:00 2001 From: Chris Mason Date: Wed, 27 May 2026 11:00:11 -0400 Subject: [PATCH] svcrdma: Fix unmatched rn_unregister on failed accept When svc_rdma_accept() takes the errout path before rpcrdma_rn_register() has succeeded, the existing cleanup block calls rpcrdma_rn_unregister(dev, &newxprt->sc_rn) unconditionally. svcxprt_rdma is kzalloc'd, so on that path sc_rn.rn_index is 0 and sc_rn.rn_done is NULL; the unregister therefore xa_erase()s another caller's slot 0 and performs an unmatched kref_put() on the rpcrdma_device's rd_kref. The same errout also brackets the cleanup with svc_xprt_get()/ svc_xprt_put() around the kref_init() birth reference. The kref goes 1 -> 2 -> 1 and never reaches 0, so the svcxprt_rdma (and the net/ns_tracker it pinned) is leaked on every failed accept. rpcrdma_rn_register() writes rn->rn_done last, only after xa_alloc() and kref_get() have both succeeded, so rn_done == NULL is a natural "never registered" sentinel. Guard rpcrdma_rn_unregister() with an early return when rn_done is NULL, and clear rn_done before the matching xa_erase() so a repeated unregister is also a no-op. With that guard in place, the accept errout drops the kref_init() birth reference via svc_xprt_put(), which dispatches svc_rdma_free(). Teardown of sc_qp, sc_sq_cq, sc_rq_cq, and sc_pd runs under existing IS_ERR/NULL guards in svc_rdma_free(); sc_rn is covered by the new rn_done sentinel; sc_cm_id is non-NULL on every errout path because svc_rdma_accept() dereferences it above the first goto errout. svc_xprt_free() drops the module reference associated with the freed transport, and svc_handle_xprt() drops its pre-acquired reference when ->xpo_accept() returns NULL. Take a replacement module reference before svc_xprt_put() so the two module_put()s remain balanced. The rn_done guard also covers svc_rdma_free()'s non-listener call to rpcrdma_rn_unregister() for transports whose register attempt failed or never ran. Fixes: 8ac6fcae5dc0 ("svcrdma: Unregister the device if svc_rdma_accept() fails") Cc: stable@vger.kernel.org Assisted-by: kres (claude-opus-4-7) Signed-off-by: Chris Mason Acked-by: Jeff Layton Link: https://patch.msgid.link/20260527-rdma-follow-on-v1-1-1b09bd87b6cd@oracle.com Signed-off-by: Chuck Lever --- net/sunrpc/xprtrdma/ib_client.c | 24 +++++++++++++++++++- net/sunrpc/xprtrdma/svc_rdma_transport.c | 28 ++++++++++++++++++------ 2 files changed, 44 insertions(+), 8 deletions(-) diff --git a/net/sunrpc/xprtrdma/ib_client.c b/net/sunrpc/xprtrdma/ib_client.c index de49ad02053d..69166d5d9987 100644 --- a/net/sunrpc/xprtrdma/ib_client.c +++ b/net/sunrpc/xprtrdma/ib_client.c @@ -51,7 +51,11 @@ static struct rpcrdma_device *rpcrdma_get_client_data(struct ib_device *device) * to be invoked when the device is removed, unless this notification * is unregistered first. * - * On failure, a negative errno is returned. + * On failure, a negative errno is returned. rn->rn_done is left + * NULL on every failure path (it is assigned only after xa_alloc + * and kref_get have both succeeded), so the @rn may safely be + * passed to rpcrdma_rn_unregister() without a separate + * registered/unregistered flag in the caller. */ int rpcrdma_rn_register(struct ib_device *device, struct rpcrdma_notification *rn, @@ -83,6 +87,10 @@ static void rpcrdma_rn_release(struct kref *kref) * rpcrdma_rn_unregister - stop device removal notifications * @device: monitored device * @rn: notification object that no longer wishes to be notified + * + * It is safe to call this on an @rn whose registration never + * completed or failed; rn_done == NULL is treated as + * never-registered and the call is a no-op. */ void rpcrdma_rn_unregister(struct ib_device *device, struct rpcrdma_notification *rn) @@ -92,6 +100,20 @@ void rpcrdma_rn_unregister(struct ib_device *device, if (!rd) return; + /* + * rn_done is the registration sentinel: rpcrdma_rn_register + * assigns it last, after xa_alloc and kref_get have both + * succeeded. A NULL rn_done means this notification was + * never registered (or its registration failed) or has + * already been unregistered, and the call is a no-op. + * Without this guard, rn_index == 0 from a kzalloc'd + * parent would erase another caller's slot 0 and underflow + * rd_kref. + */ + if (!rn->rn_done) + return; + rn->rn_done = NULL; + trace_rpcrdma_client_unregister(device, rn); xa_erase(&rd->rd_xa, rn->rn_index); kref_put(&rd->rd_kref, rpcrdma_rn_release); diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c index 7ca71741106b..9268b6105a74 100644 --- a/net/sunrpc/xprtrdma/svc_rdma_transport.c +++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c @@ -43,6 +43,7 @@ */ #include +#include #include #include #include @@ -598,13 +599,26 @@ static struct svc_xprt *svc_rdma_accept(struct svc_xprt *xprt) return &newxprt->sc_xprt; errout: - /* Take a reference in case the DTO handler runs */ - svc_xprt_get(&newxprt->sc_xprt); - if (newxprt->sc_qp && !IS_ERR(newxprt->sc_qp)) - ib_destroy_qp(newxprt->sc_qp); - rdma_destroy_id(newxprt->sc_cm_id); - rpcrdma_rn_unregister(dev, &newxprt->sc_rn); - /* This call to put will destroy the transport */ + /* + * Drop the kref_init birth reference. svc_xprt_free will + * dispatch xpo_free = svc_rdma_free, which tears down sc_qp, + * sc_sq_cq, sc_rq_cq, and sc_pd under existing IS_ERR/NULL + * guards, and sc_rn under the rn_done sentinel guard inside + * rpcrdma_rn_unregister. + * + * sc_cm_id is destroyed unconditionally by svc_rdma_free; that + * is safe here because sc_cm_id is non-NULL by caller invariant + * on every path that reaches this errout: handle_connect_req + * installs newxprt->sc_cm_id before queueing the new xprt for + * accept, and svc_rdma_accept has already dereferenced it above + * the first goto errout. + * + * svc_handle_xprt() drops its pre-acquired module reference when + * ->xpo_accept() returns NULL. Take a replacement reference before + * freeing @newxprt, because svc_xprt_free() drops the module + * reference associated with @newxprt. + */ + __module_get(newxprt->sc_xprt.xpt_class->xcl_owner); svc_xprt_put(&newxprt->sc_xprt); return NULL; }