linux-kernel - Re: [PATCH] erofs: fix wrong kunmap when using LZMA on HIGHMEM platforms

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Date:   Mon, 6 Mar 2023 16:18:08 +0800
From:   Yue Hu <zbestahu@...il.com>
To:     Gao Xiang <hsiangkao@...ux.alibaba.com>
Cc:     linux-erofs@...ts.ozlabs.org, LKML <linux-kernel@...r.kernel.org>,
        stable@...r.kernel.org, huyue2@...lpad.com
Subject: Re: [PATCH] erofs: fix wrong kunmap when using LZMA on HIGHMEM
 platforms

On Sun,  5 Mar 2023 21:44:55 +0800
Gao Xiang <hsiangkao@...ux.alibaba.com> wrote:

> As the call trace shown, the root cause is kunmap incorrect pages:
> 
>  BUG: kernel NULL pointer dereference, address: 00000000
>  CPU: 1 PID: 40 Comm: kworker/u5:0 Not tainted 6.2.0-rc5 #4
>  Workqueue: erofs_worker z_erofs_decompressqueue_work
>  EIP: z_erofs_lzma_decompress+0x34b/0x8ac
>   z_erofs_decompress+0x12/0x14
>   z_erofs_decompress_queue+0x7e7/0xb1c
>   z_erofs_decompressqueue_work+0x32/0x60
>   process_one_work+0x24b/0x4d8
>   ? process_one_work+0x1a4/0x4d8
>   worker_thread+0x14c/0x3fc
>   kthread+0xe6/0x10c
>   ? rescuer_thread+0x358/0x358
>   ? kthread_complete_and_exit+0x18/0x18
>   ret_from_fork+0x1c/0x28
>  ---[ end trace 0000000000000000 ]---
> 
> The bug is trivial and should be fixed now.  It has no impact on
> !HIGHMEM platforms.
> 
> Fixes: 622ceaddb764 ("erofs: lzma compression support")
> Cc: <stable@...r.kernel.org> # 5.16+
> Signed-off-by: Gao Xiang <hsiangkao@...ux.alibaba.com>

Reviewed-by: Yue Hu <huyue2@...lpad.com>

> ---
>  fs/erofs/decompressor_lzma.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/erofs/decompressor_lzma.c b/fs/erofs/decompressor_lzma.c
> index 091fd5adf818..5cd612a8f858 100644
> --- a/fs/erofs/decompressor_lzma.c
> +++ b/fs/erofs/decompressor_lzma.c
> @@ -278,7 +278,7 @@ int z_erofs_lzma_decompress(struct z_erofs_decompress_req *rq,
>  		}
>  	}
>  	if (no < nrpages_out && strm->buf.out)
> -		kunmap(rq->in[no]);
> +		kunmap(rq->out[no]);
>  	if (ni < nrpages_in)
>  		kunmap(rq->in[ni]);
>  	/* 4. push back LZMA stream context to the global list */