media: mediatek: vcodec: adding lock to protect decoder context list

Add a lock for the ctx_list, to avoid accessing a NULL pointer
within the 'vpu_dec_ipi_handler' function when the ctx_list has
been deleted due to an unexpected behavior on the SCP IP block.

Hardware name: Google juniper sku16 board (DT)
pstate: 20400005 (nzCv daif +PAN -UAO -TCO BTYPE=--)
pc : vpu_dec_ipi_handler+0x58/0x1f8 [mtk_vcodec_dec]
lr : scp_ipi_handler+0xd0/0x194 [mtk_scp]
sp : ffffffc0131dbbd0
x29: ffffffc0131dbbd0 x28: 0000000000000000
x27: ffffff9bb277f348 x26: ffffff9bb242ad00
x25: ffffffd2d440d3b8 x24: ffffffd2a13ff1d4
x23: ffffff9bb7fe85a0 x22: ffffffc0133fbdb0
x21: 0000000000000010 x20: ffffff9b050ea328
x19: ffffffc0131dbc08 x18: 0000000000001000
x17: 0000000000000000 x16: ffffffd2d461c6e0
x15: 0000000000000242 x14: 000000000000018f
x13: 000000000000004d x12: 0000000000000000
x11: 0000000000000001 x10: fffffffffffffff0
x9 : ffffff9bb6e793a8 x8 : 0000000000000000
x7 : 0000000000000000 x6 : 000000000000003f
x5 : 0000000000000040 x4 : fffffffffffffff0
x3 : 0000000000000020 x2 : ffffff9bb6e79080
x1 : 0000000000000010 x0 : ffffffc0131dbc08
Call trace:
vpu_dec_ipi_handler+0x58/0x1f8 [mtk_vcodec_dec (HASH:6c3f 2)]
scp_ipi_handler+0xd0/0x194 [mtk_scp (HASH:7046 3)]
mt8183_scp_irq_handler+0x44/0x88 [mtk_scp (HASH:7046 3)]
scp_irq_handler+0x48/0x90 [mtk_scp (HASH:7046 3)]
irq_thread_fn+0x38/0x94
irq_thread+0x100/0x1c0
kthread+0x140/0x1fc
ret_from_fork+0x10/0x30
Code: 54000088 f94ca50a eb14015f 54000060 (f9400108)
---[ end trace ace43ce36cbd5c93 ]---
Kernel panic - not syncing: Oops: Fatal exception
SMP: stopping secondary CPUs
Kernel Offset: 0x12c4000000 from 0xffffffc010000000
PHYS_OFFSET: 0xffffffe580000000
CPU features: 0x08240002,2188200c
Memory Limit: none

Fixes: 655b86e ("media: mediatek: vcodec: Fix possible invalid memory access for decoder")
Signed-off-by: Yunfei Dong <yunfei.dong@mediatek.com>
Reviewed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Sebastian Fricke <sebastian.fricke@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

Author: yunfei-mtk

drivers/media/platform/mediatek/vcodec/common/mtk_vcodec_fw_vpu.c

@@ -50,12 +50,12 @@ static void mtk_vcodec_vpu_reset_dec_handler(void *priv)
 
 	dev_err(&dev->plat_dev->dev, "Watchdog timeout!!");
 
-	mutex_lock(&dev->dev_mutex);
+	mutex_lock(&dev->dev_ctx_lock);
 	list_for_each_entry(ctx, &dev->ctx_list, list) {
 		ctx->state = MTK_STATE_ABORT;
 		mtk_v4l2_vdec_dbg(0, ctx, "[%d] Change to state MTK_STATE_ABORT", ctx->id);
 	}
-	mutex_unlock(&dev->dev_mutex);
+	mutex_unlock(&dev->dev_ctx_lock);
 }
 
 static void mtk_vcodec_vpu_reset_enc_handler(void *priv)

drivers/media/platform/mediatek/vcodec/decoder/mtk_vcodec_dec_drv.c

@@ -268,7 +268,9 @@ static int fops_vcodec_open(struct file *file)
 
 	ctx->dev->vdec_pdata->init_vdec_params(ctx);
 
+	mutex_lock(&dev->dev_ctx_lock);
 	list_add(&ctx->list, &dev->ctx_list);
+	mutex_unlock(&dev->dev_ctx_lock);
 	mtk_vcodec_dbgfs_create(ctx);
 
 	mutex_unlock(&dev->dev_mutex);
@@ -311,7 +313,9 @@ static int fops_vcodec_release(struct file *file)
 	v4l2_ctrl_handler_free(&ctx->ctrl_hdl);
 
 	mtk_vcodec_dbgfs_remove(dev, ctx->id);
+	mutex_lock(&dev->dev_ctx_lock);
 	list_del_init(&ctx->list);
+	mutex_unlock(&dev->dev_ctx_lock);
 	kfree(ctx);
 	mutex_unlock(&dev->dev_mutex);
 	return 0;
@@ -404,6 +408,7 @@ static int mtk_vcodec_probe(struct platform_device *pdev)
 	for (i = 0; i < MTK_VDEC_HW_MAX; i++)
 		mutex_init(&dev->dec_mutex[i]);
 	mutex_init(&dev->dev_mutex);
+	mutex_init(&dev->dev_ctx_lock);
 	spin_lock_init(&dev->irqlock);
 
 	snprintf(dev->v4l2_dev.name, sizeof(dev->v4l2_dev.name), "%s",

drivers/media/platform/mediatek/vcodec/decoder/mtk_vcodec_dec_drv.h

@@ -241,6 +241,7 @@ struct mtk_vcodec_dec_ctx {
  *
  * @dec_mutex: decoder hardware lock
  * @dev_mutex: video_device lock
+ * @dev_ctx_lock: the lock of context list
  * @decode_workqueue: decode work queue
  *
  * @irqlock: protect data access by irq handler and work thread
@@ -282,6 +283,7 @@ struct mtk_vcodec_dec_dev {
 	/* decoder hardware mutex lock */
 	struct mutex dec_mutex[MTK_VDEC_HW_MAX];
 	struct mutex dev_mutex;
+	struct mutex dev_ctx_lock;
 	struct workqueue_struct *decode_workqueue;
 
 	spinlock_t irqlock;

drivers/media/platform/mediatek/vcodec/decoder/vdec_vpu_if.c

@@ -77,12 +77,14 @@ static bool vpu_dec_check_ap_inst(struct mtk_vcodec_dec_dev *dec_dev, struct vde
 	struct mtk_vcodec_dec_ctx *ctx;
 	int ret = false;
 
+	mutex_lock(&dec_dev->dev_ctx_lock);
 	list_for_each_entry(ctx, &dec_dev->ctx_list, list) {
 		if (!IS_ERR_OR_NULL(ctx) && ctx->vpu_inst == vpu) {
 			ret = true;
 			break;
 		}
 	}
+	mutex_unlock(&dec_dev->dev_ctx_lock);
 
 	return ret;
 }