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 35928376A0B; Tue, 21 Jul 2026 21:28:07 +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=1784669298; cv=none; b=SG9e4VGF1VnqtYixY9L4KjzACxXICj88dKhZnsrsfVTMBhlnwZ/npmdbbXJloo3mjSbN0ceP4XjKpPtVrlce6XqTnSGr6W/58f3BKdM5J6pI6feWjWzb/T9Xm9knUAyi3WnUTK4sX29YGTzewiyvsoZ79eUFJSiWAkQgM1bpqPs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784669298; c=relaxed/simple; bh=OHAV/zKOLXwcf1SIIlD1eYBuytWT4keziATZzAuuybQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=sW0ykHKmf1UTJRWllnpxtoPuZ6sWRUNAG1uoa4UzJbIBLKZL+jklU2Ziaq1sdCCSmJMPuKZ6YKzjTNQTOEnEW6bvxf/f0G+b0vuqcPCWDUkSXcilE0uul69mnkdULDeGtVKHkl+t2Zm9gzvOCOSsdtT+Y2/yVlzlWjM15k+PbRg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=nJdDRdXW; 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="nJdDRdXW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 09F0C1F00A3D; Tue, 21 Jul 2026 21:28:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784669287; bh=AcHtB7jtWpxjXWOfCME2074Qbdx9LTtz2Hjq1dsAo3M=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=nJdDRdXWVLz2mlXH60joYYTpYyt8oexRb/3wiRk/EbGJ3H6espOYoDRp0oo8msBAy iaq9tZ3ZB+gCj8if74d64v8zAjvDiY/GZqiw3+h+nRjnGiMeLDM4KyWTRdrsV0GvBF 0U0cQnD1+ge7x1MD9JXFHnh4w94dHuoziR6RARhw= 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 6.1 0471/1067] net/9p: fix race condition on rdma->state in trans_rdma.c Date: Tue, 21 Jul 2026 17:17:52 +0200 Message-ID: <20260721152435.152109117@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152424.521567757@linuxfoundation.org> References: <20260721152424.521567757@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-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 29a9292303ea30..e3ee21bbe389a5 100644 --- a/net/9p/trans_rdma.c +++ b/net/9p/trans_rdma.c @@ -241,25 +241,36 @@ 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; @@ -297,6 +308,7 @@ 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, @@ -333,7 +345,10 @@ 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