[PATCH] rpmsg: virtio: fix error handling in TX buffer wait

[Atul Akella <atul.akella@gmail.com>]

The TX buffer wait loop in rpmsg_send_offchannel_raw() ignores the
possibility of wait_event_interruptible_timeout() returning a
negative value, which happens when the wait is interrupted by a
signal. In that case the loop spins back around and re-arms the
wait instead of propagating the signal, which can stall a task
that is trying to be killed.

Separately, on a genuine timeout (return value 0) the function
returns -ERESTARTSYS, which is reserved for signal-interrupted
syscalls that the kernel may restart. A timeout is not a signal
and should not be treated as restartable; return -ETIMEDOUT
instead.

Handle both cases explicitly: return err directly when negative,
and return -ETIMEDOUT on timeout.

Fixes: bcabbccabffe ("rpmsg: add virtio-based remote processor messaging bus")
Signed-off-by: Atul Akella <atul.akella@gmail.com>
---
 drivers/rpmsg/virtio_rpmsg_bus.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c
index 1b8bb05924af..a32772d6ccbc 100644
--- a/drivers/rpmsg/virtio_rpmsg_bus.c
+++ b/drivers/rpmsg/virtio_rpmsg_bus.c
@@ -536,10 +536,13 @@ static int rpmsg_send_offchannel_raw(struct rpmsg_device *rpdev,
 					(msg = get_a_tx_buf(vrp)),
 					msecs_to_jiffies(15000));
 
+		if (err < 0)
+			return err;
+
 		/* timeout ? */
 		if (!err) {
 			dev_err(dev, "timeout waiting for a tx buffer\n");
-			return -ERESTARTSYS;
+			return -ETIMEDOUT;
 		}
 	}
 
-- 
2.51.0.windows.1