linux-kernel - Re: [PATCH v2] nvme: nvme_identify_ns

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Message-ID: <20251201062106.GA19164@lst.de>
Date: Mon, 1 Dec 2025 07:21:06 +0100
From: Christoph Hellwig <hch@....de>
To: Eugene Korenevsky <ekorenevsky@...yun.com>
Cc: Keith Busch <kbusch@...nel.org>, Jens Axboe <axboe@...nel.dk>,
	Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>,
	linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] nvme: nvme_identify_ns_descs: prevent oob

On Sat, Nov 29, 2025 at 11:03:05PM +0300, Eugene Korenevsky wrote:
> -	int status, pos, len;
> +	int status, len, remain;

Pre-existing issue, but all but len here should be unsigned.

> +	remain = NVME_IDENTIFY_DATA_SIZE;
> +	cur = data;
> +	while (remain >= sizeof(*cur)) {
>  		if (cur->nidl == 0)
>  			break;
> +		if (sizeof(*cur) + cur->nidl > remain)
> +			break;
>  
>  		len = nvme_process_ns_desc(ctrl, &info->ids, cur, &csi_seen);
>  		if (len < 0)
>  			break;
>  
>  		len += sizeof(*cur);
> +		remain -= len;
> +		cur += len;
>  	}

I don't think this works, cur is a nvme_ns_id_desc pointer, so it will
be increased by len multiplied by the size of it.

I think this would work muc heasier if you'd do away with remain,
use and just use cur locally, and instead maintain an offet;  Something
like:

	offset = 0;
	do {
		cur = data + offset;

		...

		offset += len;
	} while (offset < NVME_IDENTIFY_DATA_SIZE - sizeof(*cur));