linux-kernel - [Patch v2] media: ti-vpe: cal: fix a kernel oops when unloading module

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Date:   Fri, 6 Mar 2020 07:08:39 -0600
From:   Benoit Parrot <bparrot@...com>
To:     Hans Verkuil <hverkuil@...all.nl>
CC:     <linux-media@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        Benoit Parrot <bparrot@...com>, <stable@...r.kernel.org>
Subject: [Patch v2] media: ti-vpe: cal: fix a kernel oops when unloading module

After the switch to use v4l2_async_notifier_add_subdev() and
v4l2_async_notifier_cleanup(), unloading the ti_cal module would casue a
kernel oops.

This was root cause to the fact that v4l2_async_notifier_cleanup() tries
to kfree the asd pointer passed into v4l2_async_notifier_add_subdev().

In our case the asd reference was from a statically allocated struct.
So in effect v4l2_async_notifier_cleanup() was trying to free a pointer
that was not kalloc.

So here we switch to using a kzalloc struct instead of a static one.
To acheive this we re-order some of the calls to prevent asd allocation
from leaking.

Fixes: d079f94c9046 ("media: platform: Switch to v4l2_async_notifier_add_subdev")

Cc: stable@...r.kernel.org
Signed-off-by: Benoit Parrot <bparrot@...com>
---
Changes since v1:
- fix asd allocation leak

 drivers/media/platform/ti-vpe/cal.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/media/platform/ti-vpe/cal.c b/drivers/media/platform/ti-vpe/cal.c
index 6d4cbb8782ed..6c8f3702eac0 100644
--- a/drivers/media/platform/ti-vpe/cal.c
+++ b/drivers/media/platform/ti-vpe/cal.c
@@ -372,8 +372,6 @@ struct cal_ctx {
 	struct v4l2_subdev	*sensor;
 	struct v4l2_fwnode_endpoint	endpoint;
 
-	struct v4l2_async_subdev asd;
-
 	struct v4l2_fh		fh;
 	struct cal_dev		*dev;
 	struct cc_data		*cc;
@@ -2032,7 +2030,6 @@ static int of_cal_create_instance(struct cal_ctx *ctx, int inst)
 
 	parent = pdev->dev.of_node;
 
-	asd = &ctx->asd;
 	endpoint = &ctx->endpoint;
 
 	ep_node = NULL;
@@ -2079,8 +2076,6 @@ static int of_cal_create_instance(struct cal_ctx *ctx, int inst)
 		ctx_dbg(3, ctx, "can't get remote parent\n");
 		goto cleanup_exit;
 	}
-	asd->match_type = V4L2_ASYNC_MATCH_FWNODE;
-	asd->match.fwnode = of_fwnode_handle(sensor_node);
 
 	v4l2_fwnode_endpoint_parse(of_fwnode_handle(ep_node), endpoint);
 
@@ -2110,9 +2105,17 @@ static int of_cal_create_instance(struct cal_ctx *ctx, int inst)
 
 	v4l2_async_notifier_init(&ctx->notifier);
 
+	asd = kzalloc(sizeof(*asd), GFP_KERNEL);
+	if (!asd)
+		goto cleanup_exit;
+
+	asd->match_type = V4L2_ASYNC_MATCH_FWNODE;
+	asd->match.fwnode = of_fwnode_handle(sensor_node);
+
 	ret = v4l2_async_notifier_add_subdev(&ctx->notifier, asd);
 	if (ret) {
 		ctx_err(ctx, "Error adding asd\n");
+		kfree(asd);
 		goto cleanup_exit;
 	}
 
-- 
2.17.1