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    Subject[PATCH 4.9 041/171] i2c: bcm2835: Avoid possible NULL ptr dereference
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

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

    [ Upstream commit ababb08938df7ac245d30a58b95b94ecf8dc04fc ]

    Since commit e2474541032d ("bcm2835: Fix hang for writing messages
    larger than 16 bytes") the interrupt handler is prone to a possible
    NULL pointer dereference. This could happen if an interrupt fires
    before curr_msg is set by bcm2835_i2c_xfer_msg() and randomly occurs
    on the RPi 3. Even this is an unexpected behavior the driver must
    handle that with an error instead of a crash.

    Reported-by: Peter Robinson <pbrobinson@gmail.com>
    Fixes: e2474541032d ("bcm2835: Fix hang for writing messages larger than 16 bytes")
    Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
    Acked-by: Noralf Trønnes <noralf@tronnes.org>
    Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/i2c/busses/i2c-bcm2835.c | 4 +++-
    1 file changed, 3 insertions(+), 1 deletion(-)

    diff --git a/drivers/i2c/busses/i2c-bcm2835.c b/drivers/i2c/busses/i2c-bcm2835.c
    index f283b714aa79..7ed09865cb4b 100644
    --- a/drivers/i2c/busses/i2c-bcm2835.c
    +++ b/drivers/i2c/busses/i2c-bcm2835.c
    @@ -128,7 +128,9 @@ static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data)
    }

    if (val & BCM2835_I2C_S_DONE) {
    - if (i2c_dev->curr_msg->flags & I2C_M_RD) {
    + if (!i2c_dev->curr_msg) {
    + dev_err(i2c_dev->dev, "Got unexpected interrupt (from firmware?)\n");
    + } else if (i2c_dev->curr_msg->flags & I2C_M_RD) {
    bcm2835_drain_rxfifo(i2c_dev);
    val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
    }
    --
    2.17.1


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