[PATCH 4.19 003/346] spi: bcm2835aux: Fix use-after-free on unbind

[Greg Kroah-Hartman]

From: Lukas Wunner <lu...@wunner.de>

[ Upstream commit e13ee6cc4781edaf8c7321bee19217e3702ed481 ]

bcm2835aux_spi_remove() accesses the driver's private data after calling
spi_unregister_master() even though that function releases the last
reference on the spi_master and thereby frees the private data.

Fix by switching over to the new devm_spi_alloc_master() helper which
keeps the private data accessible until the driver has unbound.

Fixes: b9dd3f6d4172 ("spi: bcm2835aux: Fix controller unregister order")
Signed-off-by: Lukas Wunner <lu...@wunner.de>
Cc: <sta...@vger.kernel.org> # v4.4+: 5e844cc37a5c: spi: Introduce 
device-managed SPI controller allocation
Cc: <sta...@vger.kernel.org> # v4.4+: b9dd3f6d4172: spi: bcm2835aux: Fix 
controller unregister order
Cc: <sta...@vger.kernel.org> # v4.4+
Link: 
https://lore.kernel.org/r/b290b06357d0c0bdee9cecc539b840a90630f101.1605121038.git.lu...@wunner.de
Signed-off-by: Mark Brown <broo...@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 drivers/spi/spi-bcm2835aux.c |   18 ++++++------------
 1 file changed, 6 insertions(+), 12 deletions(-)

--- a/drivers/spi/spi-bcm2835aux.c
+++ b/drivers/spi/spi-bcm2835aux.c
@@ -407,7 +407,7 @@ static int bcm2835aux_spi_probe(struct p
        unsigned long clk_hz;
        int err;
 
-       master = spi_alloc_master(&pdev->dev, sizeof(*bs));
+       master = devm_spi_alloc_master(&pdev->dev, sizeof(*bs));
        if (!master) {
                dev_err(&pdev->dev, "spi_alloc_master() failed\n");
                return -ENOMEM;
@@ -439,30 +439,26 @@ static int bcm2835aux_spi_probe(struct p
        /* the main area */
        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        bs->regs = devm_ioremap_resource(&pdev->dev, res);
-       if (IS_ERR(bs->regs)) {
-               err = PTR_ERR(bs->regs);
-               goto out_master_put;
-       }
+       if (IS_ERR(bs->regs))
+               return PTR_ERR(bs->regs);
 
        bs->clk = devm_clk_get(&pdev->dev, NULL);
        if ((!bs->clk) || (IS_ERR(bs->clk))) {
-               err = PTR_ERR(bs->clk);
                dev_err(&pdev->dev, "could not get clk: %d\n", err);
-               goto out_master_put;
+               return PTR_ERR(bs->clk);
        }
 
        bs->irq = platform_get_irq(pdev, 0);
        if (bs->irq <= 0) {
                dev_err(&pdev->dev, "could not get IRQ: %d\n", bs->irq);
-               err = bs->irq ? bs->irq : -ENODEV;
-               goto out_master_put;
+               return bs->irq ? bs->irq : -ENODEV;
        }
 
        /* this also enables the HW block */
        err = clk_prepare_enable(bs->clk);
        if (err) {
                dev_err(&pdev->dev, "could not prepare clock: %d\n", err);
-               goto out_master_put;
+               return err;
        }
 
        /* just checking if the clock returns a sane value */
@@ -495,8 +491,6 @@ static int bcm2835aux_spi_probe(struct p
 
 out_clk_disable:
        clk_disable_unprepare(bs->clk);
-out_master_put:
-       spi_master_put(master);
        return err;
 }