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Mon, 02 Nov 2026 04:06:10 -0800 (PST) Received: from localhost ([2c0f:3d00:6be:8900:ce5e:9212:ea4b:f30]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-6b4ec9a6f11sm3136954a12.3.2026.11.02.04.06.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Nov 2026 04:06:09 -0800 (PST) Date: Mon, 2 Nov 2026 15:06:05 +0300 From: Dan Carpenter To: Maritu Hone Cc: gregkh@linuxfoundation.org, linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org, outreachy-kernel@googlegroups.com Subject: Re: [PATCH] staging: axis-fifo: fix integer underflow in TX size check Message-ID: References: <20261102114451.54579-1-marehone12@gmail.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261102114451.54579-1-marehone12@gmail.com> On Mon, Nov 02, 2026 at 02:44:51PM +0300, Maritu Hone wrote: > fifo->tx_fifo_depth is an unsigned int parsed from the devicetree > property "xlnx,tx-fifo-depth" with no lower-bound validation. > The > write() packet-size check subtracts 4 from it: > > words_to_write > (fifo->tx_fifo_depth - 4) > > If tx_fifo_depth is less than 4, this subtraction underflows and > wraps around to a value near UINT_MAX, so the check that is supposed > to reject oversized writes never triggers, regardless of how large > words_to_write actually is. > > Reject the write up front when tx_fifo_depth is below the minimum > required by the hardware, before the subtraction can underflow. > > Fixes: 52ff2b840bc7 ("staging: axis-fifo: fix maximum TX packet length check") > Signed-off-by: Maritu Hone > --- This patch has been rejected many times before. Best to do a search on lore.kernel.org before sending patches. Device trees are trusted. I wonder if the AI is actually searching the device trees and not finding anything, so it thinks maybe the device tree is wrong? $ git grep xlnx,tx-fifo-depth | cat drivers/staging/axis-fifo/axis-fifo.c: ret = of_property_read_u32(node, "xlnx,tx-fifo-depth", drivers/staging/axis-fifo/axis-fifo.txt:- xlnx,tx-fifo-depth: Depth of TX FIFO in words drivers/staging/axis-fifo/axis-fifo.txt: xlnx,tx-fifo-depth = <0x8000>; regards, dan carpenter