From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Eddie Wai" Subject: [PATCH v3] BNX2I: Fixed kernel panic due to illegal usage of sc->request->cpu Date: Fri, 15 Jul 2011 11:17:26 -0700 Message-ID: <1310753846-4423-1-git-send-email-eddie.wai@broadcom.com> References: Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Received: from mms2.broadcom.com ([216.31.210.18]:3652 "EHLO mms2.broadcom.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755753Ab1GOSSJ (ORCPT ); Fri, 15 Jul 2011 14:18:09 -0400 In-Reply-To: Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: James Bottomley Cc: Mike Christie , open-iscsi , linux-scsi , Michael Chan , Anil Veerabhadrappa , Ben Li , Eddie Wai A kernel panic was observed when passing the sc->request->cpu = -1 to retrieve the per_cpu variable pointer: #0 [ffff880011203960] machine_kexec at ffffffff81022bc3 #1 [ffff8800112039b0] crash_kexec at ffffffff81088630 #2 [ffff880011203a80] __die at ffffffff8139ea20 #3 [ffff880011203aa0] no_context at ffffffff8102f3a7 #4 [ffff880011203ae0] __bad_area_nosemaphore at ffffffff8102f665 #5 [ffff880011203ba0] retint_signal at ffffffff8139dd1f #6 [ffff880011203cc8] bnx2i_indicate_kcqe at ffffffffa03dc4f2 #7 [ffff880011203da8] service_kcqes at ffffffffa03cb04f #8 [ffff880011203e68] cnic_service_bnx2x_kcq at ffffffffa03cb14a #9 [ffff880011203e88] cnic_service_bnx2x_bh at ffffffffa03cb1b3 The problem lies in the slow path sg_io (and perhaps sg_scsi_ioctl) call to blk_get_request->get_request/wait->blk_alloc_request->blk_rq_init which re-initializes the request->cpu to -1. There is no assignment for cpu from that to the request_fn call to low level drivers. When this happens, the sc->request->cpu will be using the init value of -1. This will create a kernel panic when it hits bnx2i because the code refers it to get the per_cpu variables ptr. This change is to put in a guard against that and also for cases when bio affinity/queue completion to the same cpu is not enabled. In those cases, the request->cpu will remain a -1 also. This bug was created from commit: b5cf6b63f73abdc051035f0050b367beeb2ef94c For the case when the blk layer did not setup the request->cpu, bnx2i will complete the sc with the current CPU of the thread. Signed-off-by: Eddie Wai --- drivers/scsi/bnx2i/bnx2i_hwi.c | 8 +++++++- 1 files changed, 7 insertions(+), 1 deletions(-) diff --git a/drivers/scsi/bnx2i/bnx2i_hwi.c b/drivers/scsi/bnx2i/bnx2i_hwi.c index 54978c1..28c6693 100644 --- a/drivers/scsi/bnx2i/bnx2i_hwi.c +++ b/drivers/scsi/bnx2i/bnx2i_hwi.c @@ -1901,6 +1901,7 @@ static int bnx2i_queue_scsi_cmd_resp(struct iscsi_session *session, struct iscsi_task *task; struct scsi_cmnd *sc; int rc = 0; + int cpu; spin_lock(&session->lock); task = iscsi_itt_to_task(bnx2i_conn->cls_conn->dd_data, @@ -1912,7 +1913,12 @@ static int bnx2i_queue_scsi_cmd_resp(struct iscsi_session *session, sc = task->sc; spin_unlock(&session->lock); - p = &per_cpu(bnx2i_percpu, sc->request->cpu); + if (!blk_rq_cpu_valid(sc->request)) + cpu = smp_processor_id(); + else + cpu = sc->request->cpu; + + p = &per_cpu(bnx2i_percpu, cpu); spin_lock(&p->p_work_lock); if (unlikely(!p->iothread)) { rc = -EINVAL; -- 1.7.0.5