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Subject[RFC PATCH 08/13] driver core: firmware loader: fix device lifetime
Date
Callers of request_firmware* must hold the reference count of
@device, otherwise it is easy to trigger oops since the firmware
loader device is the child of @device.

This patch adds comments about the usage. In fact, most of drivers
call request_firmware* in its probe() or open(), so the constraint
should be reasonable and satisfied easily.

Also this patch holds the reference cound of @device before
schedule_work() in request_firmware_nowait() to avoid that
the @device dies after request_firmware_nowait returns and before
the work is scheduled.

Also request_firmware_nowait should be called in atomic context now,
so fix the obsolete comments.

Signed-off-by: Ming Lei <ming.lei@canonical.com>
---
drivers/base/firmware_class.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
index 674cb11..540b2e1 100644
--- a/drivers/base/firmware_class.c
+++ b/drivers/base/firmware_class.c
@@ -717,6 +717,8 @@ err_put_dev:
* @name will be used as $FIRMWARE in the uevent environment and
* should be distinctive enough not to be confused with any other
* firmware image for this or any other device.
+ *
+ * Caller must hold the reference count of @device.
**/
int
request_firmware(const struct firmware **firmware_p, const char *name,
@@ -798,6 +800,7 @@ static void request_firmware_work_func(struct work_struct *work)

out:
fw_work->cont(fw, fw_work->context);
+ put_device(fw_work->device);

module_put(fw_work->module);
kfree(fw_work);
@@ -816,9 +819,10 @@ static void request_firmware_work_func(struct work_struct *work)
* @cont: function will be called asynchronously when the firmware
* request is over.
*
+ * Caller must hold the reference count of @device.
+ *
* Asynchronous variant of request_firmware() for user contexts where
- * it is not possible to sleep for long time. It can't be called
- * in atomic contexts.
+ * it is not possible to sleep for long time.
**/
int
request_firmware_nowait(
@@ -844,6 +848,7 @@ request_firmware_nowait(
return -EFAULT;
}

+ get_device(fw_work->device);
INIT_WORK(&fw_work->work, request_firmware_work_func);
schedule_work(&fw_work->work);
return 0;
--
1.7.9.5


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