Hi Sujit,
On Tue, Nov 02, 2021 at 04:51:49PM -0700, Sujit Kautkar wrote:
> qcom_glink_rpdev_release() sets channel->rpdev to NULL. However, with
> debug enabled kernel, qcom_glink_rpdev_release() gets delayed due to
> delayed kobject release and channel gets released by that time and
> triggers below kernel warning. To avoid this use-after-free, clear ept
> pointers during ept destroy and channel release and add a new condition
> in qcom_glink_rpdev_release() to access channel
>
> | BUG: KASAN: use-after-free in qcom_glink_rpdev_release+0x54/0x70
> | Write of size 8 at addr ffffffaba438e8d0 by task kworker/6:1/54
> |
> | CPU: 6 PID: 54 Comm: kworker/6:1 Not tainted 5.4.109-lockdep #16
> | Hardware name: Google Lazor (rev3+) with KB Backlight (DT)
> | Workqueue: events kobject_delayed_cleanup
> | Call trace:
> | dump_backtrace+0x0/0x284
> | show_stack+0x20/0x2c
> | dump_stack+0xd4/0x170
> | print_address_description+0x3c/0x4a8
> | __kasan_report+0x144/0x168
> | kasan_report+0x10/0x18
> | __asan_report_store8_noabort+0x1c/0x24
> | qcom_glink_rpdev_release+0x54/0x70
> | device_release+0x68/0x14c
> | kobject_delayed_cleanup+0x158/0x2cc
> | process_one_work+0x7cc/0x10a4
> | worker_thread+0x80c/0xcec
> | kthread+0x2a8/0x314
> | ret_from_fork+0x10/0x18
>
> Signed-off-by: Sujit Kautkar <sujitka@xxxxxxxxxxxx>
> ---
> Changes in v3:
> - Clear ept pointers and add extra conditions
>
> Changes in v2:
> - Fix typo in commit message
>
> drivers/rpmsg/qcom_glink_native.c | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/rpmsg/qcom_glink_native.c b/drivers/rpmsg/qcom_glink_native.c
> index e1444fefdd1c0..0c64a6f7a4f09 100644
> --- a/drivers/rpmsg/qcom_glink_native.c
> +++ b/drivers/rpmsg/qcom_glink_native.c
> @@ -269,6 +269,9 @@ static void qcom_glink_channel_release(struct kref *ref)
> idr_destroy(&channel->riids);
> spin_unlock_irqrestore(&channel->intent_lock, flags);
>
> + if (channel->rpdev)
> + channel->rpdev->ept = NULL;
> +
> kfree(channel->name);
> kfree(channel);
> }
> @@ -1214,6 +1217,8 @@ static void qcom_glink_destroy_ept(struct rpmsg_endpoint *ept)
> channel->ept.cb = NULL;
> spin_unlock_irqrestore(&channel->recv_lock, flags);
>
> + channel->rpdev->ept = NULL;
> +
> /* Decouple the potential rpdev from the channel */
> channel->rpdev = NULL;
>
> @@ -1371,9 +1376,12 @@ static const struct rpmsg_endpoint_ops glink_endpoint_ops = {
> static void qcom_glink_rpdev_release(struct device *dev)
> {
> struct rpmsg_device *rpdev = to_rpmsg_device(dev);
> - struct glink_channel *channel = to_glink_channel(rpdev->ept);
> + struct glink_channel *channel = NULL;
no need to initialize the pointer, it is assigned in the path that uses it.
>
> - channel->rpdev = NULL;
> + if (rpdev->ept) {
> + channel = to_glink_channel(rpdev->ept);
> + channel->rpdev = NULL;
> + }
> kfree(rpdev);
> }
Looks like this is already fixed in -next by:
commit 343ba27b6f9d473ec3e602cc648300eb03a7fa05
Author: Chris Lew <clew@xxxxxxxxxxxxxx>
Date: Thu Jul 30 10:48:15 2020 +0530
rpmsg: glink: Remove channel decouple from rpdev release
If a channel is being rapidly restarting and the kobj release worker is
busy, there is a chance the rpdev_release function will run after the
channel struct itself has been released.
There should not be a need to decouple the channel from rpdev in the
rpdev release since that should only happen from the close commands.
Signed-off-by: Chris Lew <clew@xxxxxxxxxxxxxx>
Signed-off-by: Deepak Kumar Singh <deesin@xxxxxxxxxxxxxx>
Signed-off-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
Link: https://lore.kernel.org/r/1596086296-28529-6-git-send-email-deesin@xxxxxxxxxxxxxx
