From 87bf646921430e303176edc4eb07c30160361b73 Mon Sep 17 00:00:00 2001 From: Li Zhijian Date: Tue, 20 Jan 2026 15:44:37 +0800 Subject: [PATCH] RDMA/rxe: Fix race condition in QP timer handlers I encontered the following warning: WARNING: drivers/infiniband/sw/rxe/rxe_task.c:249 at rxe_sched_task+0x1c8/0x238 [rdma_rxe], CPU#0: swapper/0/0 ... libsha1 [last unloaded: ip6_udp_tunnel] CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Tainted: G C 6.19.0-rc5-64k-v8+ #37 PREEMPT Tainted: [C]=CRAP Hardware name: Raspberry Pi 4 Model B Rev 1.2 Call trace: rxe_sched_task+0x1c8/0x238 [rdma_rxe] (P) retransmit_timer+0x130/0x188 [rdma_rxe] call_timer_fn+0x68/0x4d0 __run_timers+0x630/0x888 ... WARNING: drivers/infiniband/sw/rxe/rxe_task.c:38 at rxe_sched_task+0x1c0/0x238 [rdma_rxe], CPU#0: swapper/0/0 ... WARNING: drivers/infiniband/sw/rxe/rxe_task.c:111 at do_work+0x488/0x5c8 [rdma_rxe], CPU#3: kworker/u17:4/93400 ... refcount_t: underflow; use-after-free. WARNING: lib/refcount.c:28 at refcount_warn_saturate+0x138/0x1a0, CPU#3: kworker/u17:4/93400 The issue is caused by a race condition between retransmit_timer() and rxe_destroy_qp, leading to the Queue Pair's (QP) reference count dropping to zero during timer handler execution. It seems this warning is harmless because rxe_qp_do_cleanup() will flush all pending timers and requests. Example of flow causing the issue: CPU0 CPU1 retransmit_timer() { spin_lock_irqsave rxe_destroy_qp() __rxe_cleanup() __rxe_put() // qp->ref_count decrease to 0 rxe_qp_do_cleanup() { if (qp->valid) { rxe_sched_task() { WARN_ON(rxe_read(task->qp) <= 0); } } spin_unlock_irqrestore } spin_lock_irqsave qp->valid = 0 spin_unlock_irqrestore } Ensure the QP's reference count is maintained and its validity is checked within the timer callbacks by adding calls to rxe_get(qp) and corresponding rxe_put(qp) after use. Signed-off-by: Li Zhijian Fixes: d94671632572 ("RDMA/rxe: Rewrite rxe_task.c") Link: https://patch.msgid.link/20260120074437.623018-1-lizhijian@fujitsu.com Reviewed-by: Zhu Yanjun Signed-off-by: Leon Romanovsky --- drivers/infiniband/sw/rxe/rxe_comp.c | 3 +++ drivers/infiniband/sw/rxe/rxe_req.c | 3 +++ 2 files changed, 6 insertions(+) diff --git a/drivers/infiniband/sw/rxe/rxe_comp.c b/drivers/infiniband/sw/rxe/rxe_comp.c index a5b2b62f596b0..1390e861bd1d7 100644 --- a/drivers/infiniband/sw/rxe/rxe_comp.c +++ b/drivers/infiniband/sw/rxe/rxe_comp.c @@ -119,12 +119,15 @@ void retransmit_timer(struct timer_list *t) rxe_dbg_qp(qp, "retransmit timer fired\n"); + if (!rxe_get(qp)) + return; spin_lock_irqsave(&qp->state_lock, flags); if (qp->valid) { qp->comp.timeout = 1; rxe_sched_task(&qp->send_task); } spin_unlock_irqrestore(&qp->state_lock, flags); + rxe_put(qp); } void rxe_comp_queue_pkt(struct rxe_qp *qp, struct sk_buff *skb) diff --git a/drivers/infiniband/sw/rxe/rxe_req.c b/drivers/infiniband/sw/rxe/rxe_req.c index 373b03f223beb..12d03f390b097 100644 --- a/drivers/infiniband/sw/rxe/rxe_req.c +++ b/drivers/infiniband/sw/rxe/rxe_req.c @@ -102,6 +102,8 @@ void rnr_nak_timer(struct timer_list *t) rxe_dbg_qp(qp, "nak timer fired\n"); + if (!rxe_get(qp)) + return; spin_lock_irqsave(&qp->state_lock, flags); if (qp->valid) { /* request a send queue retry */ @@ -110,6 +112,7 @@ void rnr_nak_timer(struct timer_list *t) rxe_sched_task(&qp->send_task); } spin_unlock_irqrestore(&qp->state_lock, flags); + rxe_put(qp); } static void req_check_sq_drain_done(struct rxe_qp *qp) -- 2.47.3