linux-kernel - [PATCH AUTOSEL for 3.18 012/101] sparc64: ldc abort during vds iso boot

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Message-ID: <20180409003505.164715-12-alexander.levin@microsoft.com>
Date:   Mon, 9 Apr 2018 00:35:19 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Jag Raman <jag.raman@...cle.com>,
        "David S . Miller" <davem@...emloft.net>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL for 3.18 012/101] sparc64: ldc abort during vds iso
 boot

From: Jag Raman <jag.raman@...cle.com>

[ Upstream commit 6c95483b768c62f8ee933ae08a1bdbcb78b5410f ]

Orabug: 20902628

When an ldc control-only packet is received during data exchange in
read_nonraw(), a new rx head is calculated but the rx queue head is not
actually advanced (rx_set_head() is not called) and a branch is taken to
'no_data' at which point two things can happen depending on the value
of the newly calculated rx head and the current rx tail:

- If the rx queue is determined to be not empty, then the wrong packet
  is picked up.

- If the rx queue is determined to be empty, then a read error (EAGAIN)
  is eventually returned since it is falsely assumed that more data was
  expected.

The fix is to update the rx head and return in case of a control only
packet during data exchange.

Signed-off-by: Jagannathan Raman <jag.raman@...cle.com>
Reviewed-by: Aaron Young <aaron.young@...cle.com>
Reviewed-by: Alexandre Chartre <alexandre.chartre@...cle.com>
Reviewed-by: Bijan Mottahedeh <bijan.mottahedeh@...cle.com>
Reviewed-by: Liam Merwick <liam.merwick@...cle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 arch/sparc/kernel/ldc.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/sparc/kernel/ldc.c b/arch/sparc/kernel/ldc.c
index 71762565513e..8bca543977fe 100644
--- a/arch/sparc/kernel/ldc.c
+++ b/arch/sparc/kernel/ldc.c
@@ -1693,9 +1693,14 @@ static int read_nonraw(struct ldc_channel *lp, void *buf, unsigned int size)
 
 		lp->rcv_nxt = p->seqid;
 
+		/*
+		 * If this is a control-only packet, there is nothing
+		 * else to do but advance the rx queue since the packet
+		 * was already processed above.
+		 */
 		if (!(p->type & LDC_DATA)) {
 			new = rx_advance(lp, new);
-			goto no_data;
+			break;
 		}
 		if (p->stype & (LDC_ACK | LDC_NACK)) {
 			err = data_ack_nack(lp, p);
-- 
2.15.1