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Message-ID: <438a8b44-ea5f-4e13-bd7e-e1c2e2a481c4@kernel.dk>
Date: Mon, 4 Dec 2023 09:36:31 -0700
From: Jens Axboe <axboe@...nel.dk>
To: Sumit Garg <sumit.garg@...aro.org>,
Arnaud POULIQUEN <arnaud.pouliquen@...s.st.com>,
Al Viro <viro@...iv.linux.org.uk>
Cc: Jens Wiklander <jens.wiklander@...aro.org>,
Christoph Hellwig <hch@...radead.org>,
op-tee@...ts.trustedfirmware.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] tee: Use iov_iter to better support shared buffer
registration
On 12/4/23 5:42 AM, Sumit Garg wrote:
> IMO, access_ok() should be the first thing that import_ubuf() or
> import_single_range() should do, something as follows:
>
> diff --git a/lib/iov_iter.c b/lib/iov_iter.c
> index 8ff6824a1005..4aee0371824c 100644
> --- a/lib/iov_iter.c
> +++ b/lib/iov_iter.c
> @@ -1384,10 +1384,10 @@ EXPORT_SYMBOL(import_single_range);
>
> int import_ubuf(int rw, void __user *buf, size_t len, struct iov_iter *i)
> {
> - if (len > MAX_RW_COUNT)
> - len = MAX_RW_COUNT;
> if (unlikely(!access_ok(buf, len)))
> return -EFAULT;
> + if (len > MAX_RW_COUNT)
> + len = MAX_RW_COUNT;
>
> iov_iter_ubuf(i, rw, buf, len);
> return 0;
>
> Jens A., Al Viro,
>
> Was there any particular reason which I am unaware of to perform
> access_ok() check on modified input length?
This change makes sense to me, and seems consistent with what is done
elsewhere too.
--
Jens Axboe
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