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spi: fix use-after-free at controller deregistration

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The controller is typically freed as part of device_unregister() so
store the bus id before deregistration to avoid use-after-free when the
id is later released.

Fixes: 9b61e30221 ("spi: Pick spi bus number from Linux idr or spi alias")
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable <stable@vger.kernel.org>
This commit is contained in:
Johan Hovold 2017-10-30 11:35:25 +01:00 committed by Mark Brown
parent 2bd6bf03f4
commit 67f7b2781f
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GPG Key ID: 24D68B725D5487D0
1 changed files with 3 additions and 2 deletions
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5
drivers/spi/spi.c
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@ -2240,11 +2240,12 @@ static int __unregister(struct device *dev, void *null)
void spi_unregister_controller(struct spi_controller *ctlr)
{
struct spi_controller *found;
int id = ctlr->bus_num;
int dummy;
/* First make sure that this controller was ever added */
mutex_lock(&board_lock);
found = idr_find(&spi_master_idr, ctlr->bus_num);
found = idr_find(&spi_master_idr, id);
mutex_unlock(&board_lock);
if (found != ctlr) {
dev_dbg(&ctlr->dev,
@ -2264,7 +2265,7 @@ void spi_unregister_controller(struct spi_controller *ctlr)
device_unregister(&ctlr->dev);
/* free bus id */
mutex_lock(&board_lock);
idr_remove(&spi_master_idr, ctlr->bus_num);
idr_remove(&spi_master_idr, id);
mutex_unlock(&board_lock);
}
EXPORT_SYMBOL_GPL(spi_unregister_controller);