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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Kirill Kapranov <kirill.kapranov@compulab.co.il>,
        Mark Brown <broonie@kernel.org>
Subject: [PATCH 4.18 46/88] spi: fix IDR collision on systems with both fixed and dynamic SPI bus numbers
Date:   Thu, 27 Sep 2018 11:03:27 +0200
Message-Id: <20180927090306.382094027@linuxfoundation.org>
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4.18-stable review patch.  If anyone has any objections, please let me know.

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

From: Kirill Kapranov <kirill.kapranov@compulab.co.il>

commit 1a4327fbf4554d5b78d75b19a13d40d6de220159 upstream.

On systems where some controllers get a dynamic ID assigned and some have
a fixed number (e.g. from ACPI tables), the current implementation might
run into an IDR collision: in case of a fixed bus number is gotten by a
driver (but not marked busy in IDR tree) and a driver with dynamic bus
number gets the same ID and predictably fails.

Fix this by means of checking-in fixed IDsin IDR as far as dynamic ones
at the moment of the controller registration.

Fixes: 9b61e302210e (spi: Pick spi bus number from Linux idr or spi alias)
Signed-off-by: Kirill Kapranov <kirill.kapranov@compulab.co.il>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/spi/spi.c |    9 +++++++++
 1 file changed, 9 insertions(+)

--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -2170,6 +2170,15 @@ int spi_register_controller(struct spi_c
 		if (WARN(id < 0, "couldn't get idr"))
 			return id;
 		ctlr->bus_num = id;
+	} else {
+		/* devices with a fixed bus num must check-in with the num */
+		mutex_lock(&board_lock);
+		id = idr_alloc(&spi_master_idr, ctlr, ctlr->bus_num,
+			ctlr->bus_num + 1, GFP_KERNEL);
+		mutex_unlock(&board_lock);
+		if (WARN(id < 0, "couldn't get idr"))
+			return id == -ENOSPC ? -EBUSY : id;
+		ctlr->bus_num = id;
 	}
 	INIT_LIST_HEAD(&ctlr->queue);
 	spin_lock_init(&ctlr->queue_lock);