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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-489201cde98sm352987615e9.7.2026.04.24.08.15.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 24 Apr 2026 08:15:59 -0700 (PDT) Date: Fri, 24 Apr 2026 16:15:58 +0100 From: David Laight To: Zhan Xusheng Cc: Konstantin Komarov , linux-kernel@vger.kernel.org, Zhan Xusheng Subject: Re: [PATCH] fs/ntfs3: reject evcn == U64_MAX in mi_enum_attr() Message-ID: <20260424161558.2d21b624@pumpkin> In-Reply-To: <20260424132031.299385-1-zhanxusheng@xiaomi.com> References: <20260424102024.74d20552@pumpkin> <20260424132031.299385-1-zhanxusheng@xiaomi.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 24 Apr 2026 21:20:31 +0800 Zhan Xusheng wrote: > Hi David, > > That would reject the svcn == evcn case, which represents a > single-cluster extent (e.g. svcn=0, evcn=0) and is currently > treated as valid. Slight brain fade.. > > The original check allows svcn == evcn + 1 (empty range), so the > condition is strictly "greater than", not "greater than or equal". > > The issue here is the overflow of (evcn + 1) when evcn == U64_MAX, > which turns the check into "svcn > 0" and incorrectly allows > svcn == 0. Is that analysis correct? with the current code: If evcn is 2 then everything except 0, 1, 2 and 3 are errors. If evcn is -3 then only -1 is an error. If evcn is -2 no values are errors. If evcn is -1 then all svcn values except 0 are errors. Clearly this doesn't make sense if evcn is -1. But there isn't an obvious reason why svcn == -4, evcn == -1 shouldn't be a valid range. (There might be a sanity upper limit is evcn for other reasons.) David > > My patch preserves the existing semantics and only adds the > missing U64_MAX guard. > > Thanks, > Zhan Xusheng >