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Fri, 11 Apr 2025 08:07:43 -0700 (PDT) MIME-Version: 1.0 References: <20250410035717.473207-1-bhe@redhat.com> <20250410035717.473207-2-bhe@redhat.com> <20250410204338.4b2101afdf18d8898390ef58@linux-foundation.org> In-Reply-To: From: Andreas Gruenbacher Date: Fri, 11 Apr 2025 17:07:32 +0200 X-Gm-Features: ATxdqUHXErCdiRkEhF36CcQgwOHHQJ4vauPwTGL6_wmpxLHi-chD_wBZ4Y_HerY Message-ID: Subject: Re: [PATCH v4 1/4] mm/gup: fix wrongly calculated returned value in fault_in_safe_writeable() To: Baoquan He Cc: Andrew Morton , gfs2@lists.linux.dev, linux-mm@kvack.org, david@redhat.com, osalvador@suse.de, yanjun.zhu@linux.dev, linux-kernel@vger.kernel.org X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: FApOFyor3e-7AMYEuSSBrA-M8kc7qOVMsR7UStbdgMY_1744384064 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam01 X-Stat-Signature: sm331cd4tj3e7e3rcwbg9cbq7i1q6pmb X-Rspam-User: X-Rspamd-Queue-Id: D4E704000C X-HE-Tag: 1744384066-470289 X-HE-Meta: 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 7E0e7PzW LXvFWbn0htRFYtIqf5qlIoOMqth5Jqvv3Y2yoenxUYiw1p3/uIn86S2lViDyTzB+v4S8m X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Apr 11, 2025 at 7:32=E2=80=AFAM Baoquan He wrote: > On 04/10/25 at 08:43pm, Andrew Morton wrote: > > On Thu, 10 Apr 2025 11:57:14 +0800 Baoquan He wrote: > > > > > Not like fault_in_readable() or fault_in_writeable(), in > > > fault_in_safe_writeable() local variable 'start' is increased page > > > by page to loop till the whole address range is handled. However, > > > it mistakenly calcalates the size of handled range with 'uaddr - star= t'. > > > > What are the userspace-visible runtime effects of this change? > > I see it mainly affect gfs2_file_direct_read(). Not sure if GFS2 people > can sense any exceptional behaviour caused by this code bug. Thanks for the heads up. In gfs2, fault_in_iov_iter_writeable() is used in gfs2_file_direct_read() and gfs2_file_read_iter(), so this potentially affects buffered as well as direct reads. This bug could cause those gfs2 functions to spin in a loop. Can this fix please be sent to Linus for inclusion into 6.15? Thanks, Andreas