From 49b30a64d320b23d7c3a3a67f2501a6ab5518a29 Mon Sep 17 00:00:00 2001 From: Wolfram Sang Date: Sun, 26 Jul 2020 18:16:06 +0200 Subject: i2c: rcar: avoid race when unregistering slave MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit [ Upstream commit c7c9e914f9a0478fba4dc6f227cfd69cf84a4063 ] Due to the lockless design of the driver, it is theoretically possible to access a NULL pointer, if a slave interrupt was running while we were unregistering the slave. To make this rock solid, disable the interrupt for a short time while we are clearing the interrupt_enable register. This patch is purely based on code inspection. The OOPS is super-hard to trigger because clearing SAR (the address) makes interrupts even more unlikely to happen as well. While here, reinit SCR to SDBS because this bit should always be set according to documentation. There is no effect, though, because the interface is disabled. Fixes: 7b814d852af6 ("i2c: rcar: avoid race when unregistering slave client") Signed-off-by: Wolfram Sang Reviewed-by: Niklas Söderlund Signed-off-by: Wolfram Sang Signed-off-by: Sasha Levin --- drivers/i2c/busses/i2c-rcar.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'drivers/i2c') diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c index 11d197761685..dcdce18fc706 100644 --- a/drivers/i2c/busses/i2c-rcar.c +++ b/drivers/i2c/busses/i2c-rcar.c @@ -861,12 +861,14 @@ static int rcar_unreg_slave(struct i2c_client *slave) WARN_ON(!priv->slave); - /* disable irqs and ensure none is running before clearing ptr */ + /* ensure no irq is running before clearing ptr */ + disable_irq(priv->irq); rcar_i2c_write(priv, ICSIER, 0); - rcar_i2c_write(priv, ICSCR, 0); + rcar_i2c_write(priv, ICSSR, 0); + enable_irq(priv->irq); + rcar_i2c_write(priv, ICSCR, SDBS); rcar_i2c_write(priv, ICSAR, 0); /* Gen2: must be 0 if not using slave */ - synchronize_irq(priv->irq); priv->slave = NULL; pm_runtime_put(rcar_i2c_priv_to_dev(priv)); -- cgit v1.2.3