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

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Message-ID: <a2e6510f-ffd9-060e-ab03-cdc261ecc778@ti.com>
Date:   Wed, 4 Mar 2020 11:22:26 +0200
From:   Tomi Valkeinen <tomi.valkeinen@...com>
To:     Benoit Parrot <bparrot@...com>, Hans Verkuil <hverkuil@...all.nl>
CC:     <linux-media@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>
Subject: Re: [Patch] media: ti-vpe: cal: fix a kernel oops when unloading
 module

On 04/03/2020 10:41, Tomi Valkeinen wrote:

>> Thanks, this fixes the crash for me.
>>
>> It does look a bit odd that something is allocated with kzalloc, and then it's freed somewhere 
>> inside v4l2_async_notifier_cleanup, though. But if that's how it supposed to be used, looks fine 
>> to me.
> 
> Well, sent that a few seconds too early... With this patch, I see kmemleaks.

This is caused by allocating asd for all ports, even if the port is not used, causing the allocated asd to be forgotten. Also, any error there would cause leak too.

I think something like this fixes both the unused port case and error paths:

diff --git a/drivers/media/platform/ti-vpe/cal.c b/drivers/media/platform/ti-vpe/cal.c
index a928c9d66d5d..4b89dd53d2b4 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;
@@ -2020,7 +2018,6 @@ 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;
@@ -2067,8 +2064,6 @@ 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);
 
@@ -2098,9 +2093,17 @@ 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;
 	}
 
 Tomi

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