From: Chris Mason Date: Thu, 4 Jun 2026 17:06:33 +0000 (-0400) Subject: xprtrdma: Fix ep kref imbalance on ADDR_CHANGE X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=af9b65b29af341932625c4283dc7a23cdb62688a;p=thirdparty%2Flinux.git xprtrdma: Fix ep kref imbalance on ADDR_CHANGE rpcrdma_cm_event_handler() falls through to the disconnected: label on RDMA_CM_EVENT_ADDR_CHANGE and calls rpcrdma_ep_put() with no matching get when the event arrives before RDMA_CM_EVENT_ESTABLISHED. The kref then underflows during connect teardown and rpcrdma_xprt_disconnect() operates on a freed ep. Reference counts across a normal connection lifecycle: rpcrdma_ep_create() kref_init ->1 rpcrdma_xprt_connect() ep_get ->2 (before post_recvs) RDMA_CM_EVENT_ESTABLISHED ep_get ->3 RDMA_CM_EVENT_DISCONNECTED ep_put ->2 rpcrdma_xprt_drain() ep_put ->1 rpcrdma_xprt_disconnect() tail ep_put ->0 (ep_destroy) The connect-time get in rpcrdma_xprt_connect(), taken just before rpcrdma_post_recvs() "while there are outstanding Receives," is balanced by rpcrdma_xprt_drain. ADDR_CHANGE before ESTABLISHED has no get to consume, so its put drops the count to 1 and the drain put then frees the ep while rpcrdma_xprt_disconnect() still holds a pointer to it. Fix by dispatching on the prior re_connect_status via xchg(): for prev == 0 (pre-ESTABLISHED) wake the connect waiter and return with no put; for prev == 1 call rpcrdma_force_disconnect() and return. The case-1 arm relies on the subsequent RDMA_CM_EVENT_DISCONNECTED event -- reliably delivered when rdma_disconnect() is called on a still-connected cm_id -- to balance the ESTABLISHED get; rpcrdma_xprt_drain() continues to balance only that connect-time get. Any other prior value means teardown is already in flight. Fixes: 2acc5cae2923 ("xprtrdma: Prevent dereferencing r_xprt->rx_ep after it is freed") Assisted-by: kres:claude-opus-4-7 Signed-off-by: Chris Mason Signed-off-by: Chuck Lever Signed-off-by: Anna Schumaker --- diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c index 993bc5c444a4b..7ddab4ed5d036 100644 --- a/net/sunrpc/xprtrdma/verbs.c +++ b/net/sunrpc/xprtrdma/verbs.c @@ -245,8 +245,17 @@ rpcrdma_cm_event_handler(struct rdma_cm_id *id, struct rdma_cm_event *event) complete(&ep->re_done); return 0; case RDMA_CM_EVENT_ADDR_CHANGE: - ep->re_connect_status = -ENODEV; - goto disconnected; + switch (xchg(&ep->re_connect_status, -ENODEV)) { + case 0: + goto wake_connect_worker; + case 1: + /* The later DISCONNECTED event balances the + * ESTABLISHED get; do not put here. + */ + rpcrdma_force_disconnect(ep); + return 0; + } + return 0; case RDMA_CM_EVENT_ESTABLISHED: rpcrdma_ep_get(ep); ep->re_connect_status = 1; @@ -269,7 +278,6 @@ wake_connect_worker: return 0; case RDMA_CM_EVENT_DISCONNECTED: ep->re_connect_status = -ECONNABORTED; -disconnected: rpcrdma_force_disconnect(ep); return rpcrdma_ep_put(ep); default: