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Subject[PATCH 5.0 136/238] IB/rdmavt: Fix concurrency panics in QP post_send and modify to error
Date
5.0-stable review patch.  If anyone has any objections, please let me know.

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

From: Michael J. Ruhl <michael.j.ruhl@intel.com>

commit d757c60eca9b22f4d108929a24401e0fdecda0b1 upstream.

The RC/UC code path can go through a software loopback. In this code path
the receive side QP is manipulated.

If two threads are working on the QP receive side (i.e. post_send, and
modify_qp to an error state), QP information can be corrupted.

(post_send via loopback)
set r_sge
loop
update r_sge
(modify_qp)
take r_lock
update r_sge <---- r_sge is now incorrect
(post_send)
update r_sge <---- crash, etc.
...

This can lead to one of the two following crashes:

BUG: unable to handle kernel NULL pointer dereference at (null)
IP: hfi1_copy_sge+0xf1/0x2e0 [hfi1]
PGD 8000001fe6a57067 PUD 1fd9e0c067 PMD 0
Call Trace:
ruc_loopback+0x49b/0xbc0 [hfi1]
hfi1_do_send+0x38e/0x3e0 [hfi1]
_hfi1_do_send+0x1e/0x20 [hfi1]
process_one_work+0x17f/0x440
worker_thread+0x126/0x3c0
kthread+0xd1/0xe0
ret_from_fork_nospec_begin+0x21/0x21

or:

BUG: unable to handle kernel NULL pointer dereference at 0000000000000048
IP: rvt_clear_mr_refs+0x45/0x370 [rdmavt]
PGD 80000006ae5eb067 PUD ef15d0067 PMD 0
Call Trace:
rvt_error_qp+0xaa/0x240 [rdmavt]
rvt_modify_qp+0x47f/0xaa0 [rdmavt]
ib_security_modify_qp+0x8f/0x400 [ib_core]
ib_modify_qp_with_udata+0x44/0x70 [ib_core]
modify_qp.isra.23+0x1eb/0x2b0 [ib_uverbs]
ib_uverbs_modify_qp+0xaa/0xf0 [ib_uverbs]
ib_uverbs_write+0x272/0x430 [ib_uverbs]
vfs_write+0xc0/0x1f0
SyS_write+0x7f/0xf0
system_call_fastpath+0x1c/0x21

Fix by using the appropriate locking on the receiving QP.

Fixes: 15703461533a ("IB/{hfi1, qib, rdmavt}: Move ruc_loopback to rdmavt")
Cc: <stable@vger.kernel.org> #v4.9+
Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/infiniband/sw/rdmavt/qp.c | 33 +++++++++++++++++++++++----------
1 file changed, 23 insertions(+), 10 deletions(-)

--- a/drivers/infiniband/sw/rdmavt/qp.c
+++ b/drivers/infiniband/sw/rdmavt/qp.c
@@ -2785,6 +2785,18 @@ again:
}
EXPORT_SYMBOL(rvt_copy_sge);

+static enum ib_wc_status loopback_qp_drop(struct rvt_ibport *rvp,
+ struct rvt_qp *sqp)
+{
+ rvp->n_pkt_drops++;
+ /*
+ * For RC, the requester would timeout and retry so
+ * shortcut the timeouts and just signal too many retries.
+ */
+ return sqp->ibqp.qp_type == IB_QPT_RC ?
+ IB_WC_RETRY_EXC_ERR : IB_WC_SUCCESS;
+}
+
/**
* ruc_loopback - handle UC and RC loopback requests
* @sqp: the sending QP
@@ -2857,17 +2869,14 @@ again:
}
spin_unlock_irqrestore(&sqp->s_lock, flags);

- if (!qp || !(ib_rvt_state_ops[qp->state] & RVT_PROCESS_RECV_OK) ||
+ if (!qp) {
+ send_status = loopback_qp_drop(rvp, sqp);
+ goto serr_no_r_lock;
+ }
+ spin_lock_irqsave(&qp->r_lock, flags);
+ if (!(ib_rvt_state_ops[qp->state] & RVT_PROCESS_RECV_OK) ||
qp->ibqp.qp_type != sqp->ibqp.qp_type) {
- rvp->n_pkt_drops++;
- /*
- * For RC, the requester would timeout and retry so
- * shortcut the timeouts and just signal too many retries.
- */
- if (sqp->ibqp.qp_type == IB_QPT_RC)
- send_status = IB_WC_RETRY_EXC_ERR;
- else
- send_status = IB_WC_SUCCESS;
+ send_status = loopback_qp_drop(rvp, sqp);
goto serr;
}

@@ -3047,6 +3056,7 @@ do_write:
wqe->wr.send_flags & IB_SEND_SOLICITED);

send_comp:
+ spin_unlock_irqrestore(&qp->r_lock, flags);
spin_lock_irqsave(&sqp->s_lock, flags);
rvp->n_loop_pkts++;
flush_send:
@@ -3073,6 +3083,7 @@ rnr_nak:
}
if (sqp->s_rnr_retry_cnt < 7)
sqp->s_rnr_retry--;
+ spin_unlock_irqrestore(&qp->r_lock, flags);
spin_lock_irqsave(&sqp->s_lock, flags);
if (!(ib_rvt_state_ops[sqp->state] & RVT_PROCESS_RECV_OK))
goto clr_busy;
@@ -3101,6 +3112,8 @@ err:
rvt_rc_error(qp, wc.status);

serr:
+ spin_unlock_irqrestore(&qp->r_lock, flags);
+serr_no_r_lock:
spin_lock_irqsave(&sqp->s_lock, flags);
rvt_send_complete(sqp, wqe, send_status);
if (sqp->ibqp.qp_type == IB_QPT_RC) {

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