From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7742D231829; Tue, 21 Jul 2026 18:54:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784660052; cv=none; b=WmJ7fbVqBnUZQFi/p7+vIZvRp2BxJC2mtXL61S+1TFDWnKTEt/rss+/+ikVyvK95viJL+K5C/xMo9wDumUIHUtKpwBoc8gpriYF6qrRe6TbxJR8bMrmkaedXefNwVEYdZH/OT7jHoZz9xLilsvvAgvWhChxdh9YkRpN2Ib6J1NU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784660052; c=relaxed/simple; bh=iroDmxlPvieLCJhahRdz0auFtG77O04Q+qNgU7dqrs4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=fIy3/FKn24ojZGONx4kZWIXcdWh18w0FSj1quOotPpLjETMh2L2wDr+JwhIjBRWA+ko/S8LCK9p8aQQNSba84GWLmXNxfS/TAEZwQrITo5qo919MVtdxv9D1JYrzDsT/OTeyPIiEY+xnwcjmOFFtN36TtDDP1cHurYQrGokNCGs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=zCZdAIlY; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="zCZdAIlY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DFDBD1F000E9; Tue, 21 Jul 2026 18:54:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784660051; bh=GfUz7hUBOppktsuIBYhIAWv8+ucReE6RCuZpRSXrFMk=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=zCZdAIlYdypvXoZ4sR8vid4KBYi0GvVB1RA32uzvzbHnrF6bEVBEpoMsP8SgfMgQe uN/iWc0Lvv9yLUG0HtQzUo3iy5Q5sjL+SPSCris+ufeVNa8mza3oR9Ewcx05kFv30B X7g2Xoo3oBp559G+/JygSZwHN2yKIeDgPfaDr4os= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Yizhou Zhao , Yuxiang Yang , Ao Wang , Xuewei Feng , Qi Li , Ke Xu , Dominique Martinet , Sasha Levin Subject: [PATCH 7.1 0826/2077] net/9p: fix race condition on rdma->state in trans_rdma.c Date: Tue, 21 Jul 2026 17:08:19 +0200 Message-ID: <20260721152612.270193686@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152552.646164743@linuxfoundation.org> References: <20260721152552.646164743@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Yizhou Zhao [ Upstream commit 7d54894a1ee265a72d70f7cae1da6cc774cccc71 ] The rdma->state field is modified without holding req_lock in both recv_done() and p9_cm_event_handler(), while rdma_request() accesses the same field under the req_lock spinlock. This inconsistent locking creates a race condition: - recv_done() running in softirq completion context sets rdma->state = P9_RDMA_FLUSHING without acquiring req_lock - p9_cm_event_handler() modifies rdma->state at multiple points (ADDR_RESOLVED, ROUTE_RESOLVED, ESTABLISHED, CLOSED) without req_lock - rdma_request() uses spin_lock_irqsave(&rdma->req_lock, flags) to protect the read-modify-write of rdma->state The race can cause lost state transitions: recv_done() or the CM event handler could set state to FLUSHING/CLOSED while rdma_request() is concurrently checking or modifying state under the lock, leading to the FLUSHING transition being silently overwritten by CLOSING. This corrupts the connection state machine and can cause use-after-free on RDMA request objects during teardown. Fix by adding req_lock protection to all rdma->state modifications in recv_done() and p9_cm_event_handler(), matching the pattern already used in rdma_request(). Use spin_lock_irqsave/spin_unlock_irqrestore in the CM event handler since it can race with recv_done() which runs in softirq context. Tested with a kernel module that races two threads (simulating rdma_request and recv_done/CM handler) on rdma->state with proper locking: 5.5M+ FLUSHING writes over 27M iterations with 0 lost transitions. Fixes: 473c7dd1d7b5 ("9p/rdma: remove useless check in cm_event_handler") Reported-by: Yizhou Zhao Reported-by: Yuxiang Yang Reported-by: Ao Wang Reported-by: Xuewei Feng Reported-by: Qi Li Reported-by: Ke Xu Assisted-by: GLM:GLM-5.1 Signed-off-by: Yizhou Zhao Message-ID: <20260529073933.77315-1-zhaoyz24@mails.tsinghua.edu.cn> Signed-off-by: Dominique Martinet Signed-off-by: Sasha Levin --- net/9p/trans_rdma.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) diff --git a/net/9p/trans_rdma.c b/net/9p/trans_rdma.c index aa5bd74d333f3b..b4274f10fa4487 100644 --- a/net/9p/trans_rdma.c +++ b/net/9p/trans_rdma.c @@ -128,25 +128,36 @@ p9_cm_event_handler(struct rdma_cm_id *id, struct rdma_cm_event *event) { struct p9_client *c = id->context; struct p9_trans_rdma *rdma = c->trans; + unsigned long flags; + switch (event->event) { case RDMA_CM_EVENT_ADDR_RESOLVED: + spin_lock_irqsave(&rdma->req_lock, flags); BUG_ON(rdma->state != P9_RDMA_INIT); rdma->state = P9_RDMA_ADDR_RESOLVED; + spin_unlock_irqrestore(&rdma->req_lock, flags); break; case RDMA_CM_EVENT_ROUTE_RESOLVED: + spin_lock_irqsave(&rdma->req_lock, flags); BUG_ON(rdma->state != P9_RDMA_ADDR_RESOLVED); rdma->state = P9_RDMA_ROUTE_RESOLVED; + spin_unlock_irqrestore(&rdma->req_lock, flags); break; case RDMA_CM_EVENT_ESTABLISHED: + spin_lock_irqsave(&rdma->req_lock, flags); BUG_ON(rdma->state != P9_RDMA_ROUTE_RESOLVED); rdma->state = P9_RDMA_CONNECTED; + spin_unlock_irqrestore(&rdma->req_lock, flags); break; case RDMA_CM_EVENT_DISCONNECTED: - if (rdma) + if (rdma) { + spin_lock_irqsave(&rdma->req_lock, flags); rdma->state = P9_RDMA_CLOSED; + spin_unlock_irqrestore(&rdma->req_lock, flags); + } c->status = Disconnected; break; @@ -184,6 +195,7 @@ recv_done(struct ib_cq *cq, struct ib_wc *wc) struct p9_req_t *req; int err = 0; int16_t tag; + unsigned long flags; req = NULL; ib_dma_unmap_single(rdma->cm_id->device, c->busa, client->msize, @@ -220,7 +232,10 @@ recv_done(struct ib_cq *cq, struct ib_wc *wc) err_out: p9_debug(P9_DEBUG_ERROR, "req %p err %d status %d\n", req, err, wc->status); - rdma->state = P9_RDMA_FLUSHING; + spin_lock_irqsave(&rdma->req_lock, flags); + if (rdma->state < P9_RDMA_FLUSHING) + rdma->state = P9_RDMA_FLUSHING; + spin_unlock_irqrestore(&rdma->req_lock, flags); client->status = Disconnected; goto out; } -- 2.53.0