[PATCH AUTOSEL for 4.4 145/167] sparc64: ldc abort during vds iso boot

Sasha Levin
2018-03-19T17:02:02Z

From: Jag Raman <jag.raman@oracle.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@oracle.com>
Reviewed-by: Aaron Young <aaron.young@oracle.com>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Reviewed-by: Bijan Mottahedeh <bijan.mottahedeh@oracle.com>
Reviewed-by: Liam Merwick <liam.merwick@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.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 59d503866431..9cc600b2d68c 100644
--- a/arch/sparc/kernel/ldc.c
+++ b/arch/sparc/kernel/ldc.c
@@ -1733,9 +1733,14 @@ 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);
--
2.14.1