From: Wolfram Sang wsa+renesas@sang-engineering.com
[ 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 wsa+renesas@sang-engineering.com Reviewed-by: Niklas Söderlund niklas.soderlund+renesas@ragnatech.se Signed-off-by: Wolfram Sang wsa@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/i2c/busses/i2c-rcar.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c index 3ea6013a3d68a..0b90aa0318df3 100644 --- a/drivers/i2c/busses/i2c-rcar.c +++ b/drivers/i2c/busses/i2c-rcar.c @@ -863,12 +863,14 @@ 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));