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Mon, 16 Mar 2026 12:37:36 -0700 (PDT) Message-ID: <1f79957a-5b23-4bbd-af8d-9d1c86791645@kernel.dk> Date: Mon, 16 Mar 2026 13:37:35 -0600 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] io_uring: cast id to u64 before shifting in io_allocate_rbuf_ring() To: Anas Iqbal , Pavel Begunkov Cc: io-uring@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260316150636.2123-1-mohd.abd.6602@gmail.com> Content-Language: en-US From: Jens Axboe In-Reply-To: <20260316150636.2123-1-mohd.abd.6602@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 3/16/26 9:06 AM, Anas Iqbal wrote: > Smatch warns: > io_uring/zcrx.c:393 io_allocate_rbuf_ring() warn: should 'id << 16' be a 64 bit type? > > The expression 'id << IORING_OFF_PBUF_SHIFT' is evaluated using 32-bit > arithmetic because id is a u32. This may overflow before being promoted > to the 64-bit mmap_offset. > > Cast id to u64 before shifting to ensure the shift is performed in > 64-bit arithmetic. I'd be impressed if 'id' could be large enough to cause this to overflow. AFAICT, you'd need more than 64K interface queues registered to hit this. So I think this should be reframed as a cleanup, to appease smatch. I'll defer to Pavel on that one. -- Jens Axboe