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From:   Ben Hutchings <ben@decadent.org.uk>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
CC:     akpm@linux-foundation.org,
        "Steve Wise" <swise@opengridcomputing.com>,
        "Jason Gunthorpe" <jgg@mellanox.com>
Date:   Sun, 09 Dec 2018 21:50:33 +0000
Message-ID: <lsq.1544392233.590575248@decadent.org.uk>
Subject: [PATCH 3.16 194/328] iw_cxgb4: only allow 1 flush on user qps
In-Reply-To: <lsq.1544392232.713909046@decadent.org.uk>
Sender: linux-kernel-owner@vger.kernel.org
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3.16.62-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Steve Wise <swise@opengridcomputing.com>

commit 308aa2b8f7b7db3332a7d41099fd37851fb793b2 upstream.

Once the qp has been flushed, it cannot be flushed again.  The user qp
flush logic wasn't enforcing it however.  The bug can cause
touch-after-free crashes like:

Unable to handle kernel paging request for data at address 0x000001ec
Faulting instruction address: 0xc008000016069100
Oops: Kernel access of bad area, sig: 11 [#1]
...
NIP [c008000016069100] flush_qp+0x80/0x480 [iw_cxgb4]
LR [c00800001606cd6c] c4iw_modify_qp+0x71c/0x11d0 [iw_cxgb4]
Call Trace:
[c00800001606cd6c] c4iw_modify_qp+0x71c/0x11d0 [iw_cxgb4]
[c00800001606e868] c4iw_ib_modify_qp+0x118/0x200 [iw_cxgb4]
[c0080000119eae80] ib_security_modify_qp+0xd0/0x3d0 [ib_core]
[c0080000119c4e24] ib_modify_qp+0xc4/0x2c0 [ib_core]
[c008000011df0284] iwcm_modify_qp_err+0x44/0x70 [iw_cm]
[c008000011df0fec] destroy_cm_id+0xcc/0x370 [iw_cm]
[c008000011ed4358] rdma_destroy_id+0x3c8/0x520 [rdma_cm]
[c0080000134b0540] ucma_close+0x90/0x1b0 [rdma_ucm]
[c000000000444da4] __fput+0xe4/0x2f0

So fix flush_qp() to only flush the wq once.

Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 drivers/infiniband/hw/cxgb4/qp.c | 6 ++++++
 1 file changed, 6 insertions(+)

--- a/drivers/infiniband/hw/cxgb4/qp.c
+++ b/drivers/infiniband/hw/cxgb4/qp.c
@@ -1133,6 +1133,12 @@ static void flush_qp(struct c4iw_qp *qhp
 	schp = to_c4iw_cq(qhp->ibqp.send_cq);
 
 	if (qhp->ibqp.uobject) {
+
+		/* for user qps, qhp->wq.flushed is protected by qhp->mutex */
+		if (qhp->wq.flushed)
+			return;
+
+		qhp->wq.flushed = 1;
 		t4_set_wq_in_error(&qhp->wq);
 		t4_set_cq_in_error(&rchp->cq);
 		spin_lock_irqsave(&rchp->comp_handler_lock, flag);