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Date: Fri, 15 May 2026 09:45:31 -0600
From: Keith Busch <kbusch@kernel.org>
To: Michael Bommarito <michael.bommarito@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>, io-uring@vger.kernel.org,
	Pavel Begunkov <asml.silence@gmail.com>,
	Li Zetao <lizetao1@huawei.com>, bpf@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] io_uring: propagate array_index_nospec opcode into
 req->opcode
Message-ID: <agc_m0rN3MN7ttAY@kbusch-mbp>
References: <20260515145812.1241925-1-michael.bommarito@gmail.com>
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In-Reply-To: <20260515145812.1241925-1-michael.bommarito@gmail.com>

On Fri, May 15, 2026 at 10:58:11AM -0400, Michael Bommarito wrote:
> The compiled change is one instruction (a single mov of the clamped
> byte to req->opcode); the cmp/sbb/and clamp triplet is unchanged.
> No functional change: array_index_nospec() is a no-op for opcodes in
> [0, IORING_OP_LAST), and out-of-range opcodes are still rejected at
> the bounds check above this assignment.  

Since the bounds check above already catches an invalid opcode, why does
it need to be re-initialized to the clamped value? Surely it's already
the same value if we've taken this path, no?