Re: [PATCH] rpmsg: glink: Release driver_override

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On 1/18/2023 9:50 AM, Bjorn Andersson wrote:
On Tue, Jan 17, 2023 at 05:01:01PM -0800, Chris Lew wrote:


On 1/9/2023 2:38 PM, Bjorn Andersson wrote:
Upon termination of the rpmsg_device, driver_override needs to be freed
to avoid leaking the potentially assigned string.

Fixes: 42cd402b8fd4 ("rpmsg: Fix kfree() of static memory on setting driver_override")
Fixes: 39e47767ec9b ("rpmsg: Add driver_override device attribute for rpmsg_device")
Signed-off-by: Bjorn Andersson <quic_bjorande@xxxxxxxxxxx>
---
   drivers/rpmsg/qcom_glink_native.c | 2 ++
   1 file changed, 2 insertions(+)

diff --git a/drivers/rpmsg/qcom_glink_native.c b/drivers/rpmsg/qcom_glink_native.c
index 8620eea1dc8a..046271e439c5 100644
--- a/drivers/rpmsg/qcom_glink_native.c
+++ b/drivers/rpmsg/qcom_glink_native.c
@@ -1454,6 +1454,7 @@ static void qcom_glink_rpdev_release(struct device *dev)
   {
   	struct rpmsg_device *rpdev = to_rpmsg_device(dev);
+	kfree(rpdev->driver_override);

I see in Krzysztof's original patch to fix up the driver_override we do
kfree in other areas of rpmsg.


Right, in the original patch what became driver_set_override() was open
coded and hence there was a kfree().

More of a just curious as to why don't we use the driver_set_override
function to clear the string? It's mentioned in the rpmsg header that the
helper should be used.

--- include/linux/rpmsg.h
  * @driver_override: driver name to force a match; do not set directly,
  *                   because core frees it; use driver_set_override() to
  *                   set or clear it.


Looking around the kernel, just calling kfree() in the release function
seems to be how others are doing it as well. As such I presume that
comment applies to the runtime state, rather than while we're cleaning
things up.

Regards,
Bjorn


Got it - should be safe to follow how others are handling this in cleanup.

Reviewed-by: Chris Lew <quic_clew@xxxxxxxxxxx>

   	kfree(rpdev);
   }
@@ -1697,6 +1698,7 @@ static void qcom_glink_device_release(struct device *dev)
   	/* Release qcom_glink_alloc_channel() reference */
   	kref_put(&channel->refcount, qcom_glink_channel_release);
+	kfree(rpdev->driver_override);
   	kfree(rpdev);
   }




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