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    Subject[PATCH 4.16 074/113] ARM: amba: Fix race condition with driver_override
    Date
    4.16-stable review patch.  If anyone has any objections, please let me know.

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

    From: Geert Uytterhoeven <geert+renesas@glider.be>

    commit 6a7228d90d42bcacfe38786756ba62762b91c20a upstream.

    The driver_override implementation is susceptible to a race condition
    when different threads are reading vs storing a different driver
    override. Add locking to avoid this race condition.

    Cfr. commits 6265539776a0810b ("driver core: platform: fix race
    condition with driver_override") and 9561475db680f714 ("PCI: Fix race
    condition with driver_override").

    Fixes: 3cf385713460eb2b ("ARM: 8256/1: driver coamba: add device binding path 'driver_override'")
    Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
    Reviewed-by: Todd Kjos <tkjos@google.com>
    Cc: stable <stable@vger.kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/amba/bus.c | 11 +++++++++--
    1 file changed, 9 insertions(+), 2 deletions(-)

    --- a/drivers/amba/bus.c
    +++ b/drivers/amba/bus.c
    @@ -69,8 +69,12 @@ static ssize_t driver_override_show(stru
    struct device_attribute *attr, char *buf)
    {
    struct amba_device *dev = to_amba_device(_dev);
    + ssize_t len;

    - return sprintf(buf, "%s\n", dev->driver_override);
    + device_lock(_dev);
    + len = sprintf(buf, "%s\n", dev->driver_override);
    + device_unlock(_dev);
    + return len;
    }

    static ssize_t driver_override_store(struct device *_dev,
    @@ -78,7 +82,7 @@ static ssize_t driver_override_store(str
    const char *buf, size_t count)
    {
    struct amba_device *dev = to_amba_device(_dev);
    - char *driver_override, *old = dev->driver_override, *cp;
    + char *driver_override, *old, *cp;

    if (count > PATH_MAX)
    return -EINVAL;
    @@ -91,12 +95,15 @@ static ssize_t driver_override_store(str
    if (cp)
    *cp = '\0';

    + device_lock(_dev);
    + old = dev->driver_override;
    if (strlen(driver_override)) {
    dev->driver_override = driver_override;
    } else {
    kfree(driver_override);
    dev->driver_override = NULL;
    }
    + device_unlock(_dev);

    kfree(old);


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