linux-kernel - Re: [PATCH] media: mediatek: vcodec: Fix oops when HEVC init fails

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Message-ID: <20240313140028.zk47awvadwfrutu6@basti-XPS-13-9310>
Date: Wed, 13 Mar 2024 15:00:28 +0100
From: Sebastian Fricke <sebastian.fricke@...labora.com>
To: Nicolas Dufresne <nicolas.dufresne@...labora.com>
Cc: Tiffany Lin <tiffany.lin@...iatek.com>,
	Andrew-CT Chen <andrew-ct.chen@...iatek.com>,
	Yunfei Dong <yunfei.dong@...iatek.com>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	Hans Verkuil <hverkuil-cisco@...all.nl>, kernel@...labora.com,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH] media: mediatek: vcodec: Fix oops when HEVC init fails

Hey Nicolas,

On 26.02.2024 16:19, Nicolas Dufresne wrote:
>In stateless HEVC case, the instance pointer was saved in the
>context regardless if the initialization worked. As the pointer
>is freed in failure, this resulted in use after free in the
>deinit function.

just to fix some grammatic erros in the commit log, my suggestion:

```
The stateless HEVC decoder saves the instance pointer in the context
regardless if the initialization worked or not. This caused a use after
free, when the pointer is freed in case of a failure in the deinit
function.
Only store the instance pointer when the initialization was successful,
to solve this issue.
```

Greetings,
Sebastian

>
> Hardware name: Acer Tomato (rev3 - 4) board (DT)
> pstate: 80400009 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : vcodec_vpu_send_msg+0x4c/0x190 [mtk_vcodec_dec]
> lr : vcodec_send_ap_ipi+0x78/0x170 [mtk_vcodec_dec]
> sp : ffff80008750bc20
> x29: ffff80008750bc20 x28: ffff1299f6d70000 x27: 0000000000000000
> x26: 0000000000000000 x25: 0000000000000000 x24: 0000000000000000
> x23: ffff80008750bc98 x22: 000000000000a003 x21: ffffd45c4cfae000
> x20: 0000000000000010 x19: ffff1299fd668310 x18: 000000000000001a
> x17: 000000040044ffff x16: ffffd45cb15dc648 x15: 0000000000000000
> x14: ffff1299c08da1c0 x13: ffffd45cb1f87a10 x12: ffffd45cb2f5fe80
> x11: 0000000000000001 x10: 0000000000001b30 x9 : ffffd45c4d12b488
> x8 : 1fffe25339380d81 x7 : 0000000000000001 x6 : ffff1299c9c06c00
> x5 : 0000000000000132 x4 : 0000000000000000 x3 : 0000000000000000
> x2 : 0000000000000010 x1 : ffff80008750bc98 x0 : 0000000000000000
> Call trace:
>  vcodec_vpu_send_msg+0x4c/0x190 [mtk_vcodec_dec]
>  vcodec_send_ap_ipi+0x78/0x170 [mtk_vcodec_dec]
>  vpu_dec_deinit+0x1c/0x30 [mtk_vcodec_dec]
>  vdec_hevc_slice_deinit+0x30/0x98 [mtk_vcodec_dec]
>  vdec_if_deinit+0x38/0x68 [mtk_vcodec_dec]
>  mtk_vcodec_dec_release+0x20/0x40 [mtk_vcodec_dec]
>  fops_vcodec_release+0x64/0x118 [mtk_vcodec_dec]
>  v4l2_release+0x7c/0x100
>  __fput+0x80/0x2d8
>  __fput_sync+0x58/0x70
>  __arm64_sys_close+0x40/0x90
>  invoke_syscall+0x50/0x128
>  el0_svc_common.constprop.0+0x48/0xf0
>  do_el0_svc+0x24/0x38
>  el0_svc+0x38/0xd8
>  el0t_64_sync_handler+0xc0/0xc8
>  el0t_64_sync+0x1a8/0x1b0
> Code: d503201f f9401660 b900127f b900227f (f9400400)
>
>Signed-off-by: Nicolas Dufresne <nicolas.dufresne@...labora.com>
>Fixes: 2674486aac7d ("media: mediatek: vcodec: support stateless hevc decoder")
>---
> .../mediatek/vcodec/decoder/vdec/vdec_hevc_req_multi_if.c       | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_hevc_req_multi_if.c b/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_hevc_req_multi_if.c
>index 06ed47df693bf..21836dd6ef85a 100644
>--- a/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_hevc_req_multi_if.c
>+++ b/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_hevc_req_multi_if.c
>@@ -869,7 +869,6 @@ static int vdec_hevc_slice_init(struct mtk_vcodec_dec_ctx *ctx)
> 	inst->vpu.codec_type = ctx->current_codec;
> 	inst->vpu.capture_type = ctx->capture_fourcc;
>
>-	ctx->drv_handle = inst;
> 	err = vpu_dec_init(&inst->vpu);
> 	if (err) {
> 		mtk_vdec_err(ctx, "vdec_hevc init err=%d", err);
>@@ -898,6 +897,7 @@ static int vdec_hevc_slice_init(struct mtk_vcodec_dec_ctx *ctx)
> 	mtk_vdec_debug(ctx, "lat hevc instance >> %p, codec_type = 0x%x",
> 		       inst, inst->vpu.codec_type);
>
>+	ctx->drv_handle = inst;
> 	return 0;
> error_free_inst:
> 	kfree(inst);
>-- 
>2.43.2
>
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