linux-kernel - Re: [PATCH v2] ksmbd: vfs: skip lock-range check on equal size to avoid size==0 underflow

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Message-ID: <CAKYAXd-SSBbW+FhC7mHYEh1JLFRVNyNOLiogbj=Nt1eszxf2vw@mail.gmail.com>
Date: Sun, 9 Nov 2025 10:32:37 +0900
From: Namjae Jeon <linkinjeon@...nel.org>
To: Qianchang Zhao <pioooooooooip@...il.com>
Cc: Steve French <smfrench@...il.com>, gregkh@...uxfoundation.org, 
	linux-cifs@...r.kernel.org, linux-kernel@...r.kernel.org, security@...nel.org, 
	Zhitong Liu <liuzhitong1993@...il.com>, stable@...r.kernel.org
Subject: Re: [PATCH v2] ksmbd: vfs: skip lock-range check on equal size to
 avoid size==0 underflow

On Sun, Nov 9, 2025 at 12:57 AM Qianchang Zhao <pioooooooooip@...il.com> wrote:
>
> When size equals the current i_size (including 0), the code used to call
> check_lock_range(filp, i_size, size - 1, WRITE), which computes `size - 1`
> and can underflow for size==0. Skip the equal case.
>
> Reported-by: Qianchang Zhao <pioooooooooip@...il.com>
> Reported-by: Zhitong Liu <liuzhitong1993@...il.com>
> Cc: stable@...r.kernel.org
> Signed-off-by: Qianchang Zhao <pioooooooooip@...il.com>
Applied it to #ksmbd-for-next-next.
Thanks!