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Date: Wed, 16 Apr 2025 16:55:12 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Nitesh Shetty <nj.shetty@samsung.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>, axboe@kernel.dk,
 gost.dev@samsung.com, nitheshshetty@gmail.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] iov_iter: Use iov_offset for length calculation in
 iov_iter_aligned_bvec
Message-Id: <20250416165512.990257538f61be5857e513ab@linux-foundation.org>
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References: <CGME20250415182307epcas5p4853044d013dbc943a8e54dca0f2a39c2@epcas5p4.samsung.com>
	<20250415181419.16305-1-nj.shetty@samsung.com>
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On Tue, 15 Apr 2025 23:44:19 +0530 Nitesh Shetty <nj.shetty@samsung.com> wrote:

> If iov_offset is non-zero, then we need to consider iov_offset in length
> calculation, otherwise we might pass smaller IOs such as 512 bytes
> with 256 bytes offset.
> 

Please describe the userspace-visible effects of this flaw, if any?

> --- a/lib/iov_iter.c
> +++ b/lib/iov_iter.c
> @@ -820,7 +820,7 @@ static bool iov_iter_aligned_bvec(const struct iov_iter *i, unsigned addr_mask,
>  	size_t size = i->count;
>  
>  	do {
> -		size_t len = bvec->bv_len;
> +		size_t len = bvec->bv_len - skip;
>  
>  		if (len > size)
>  			len = size;
>