From: Jag Raman <>

[ 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

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 <>
Reviewed-by: Aaron Young <>
Reviewed-by: Alexandre Chartre <>
Reviewed-by: Bijan Mottahedeh <>
Reviewed-by: Liam Merwick <>
Signed-off-by: David S. Miller <>
Signed-off-by: Sasha Levin <>
 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);

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