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Tue, 1 Apr 2025 14:00:07 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id wBo6A2fx62c1XAAAD6G6ig (envelope-from ); Tue, 01 Apr 2025 14:00:07 +0000 Date: Tue, 1 Apr 2025 16:00:05 +0200 From: Oscar Salvador To: David Hildenbrand Cc: Baoquan He , akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, yanjun.zhu@linux.dev Subject: Re: [PATCH v2 1/7] mm/gup: fix wrongly calculated returned value in fault_in_safe_writeable() Message-ID: References: <20250331081327.256412-1-bhe@redhat.com> <20250331081327.256412-2-bhe@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 2EF60160017 X-Stat-Signature: s67qwpkd6hch4b68mki4gkgoch39wdbn X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1743516008-898303 X-HE-Meta: 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 RFZhfok8 x4nvrRiLKQCKiU/tLjL+W/XlWQr/g3w2Pyg9F43fvt9GR/xv2lW8n3QG5ex5wzZ4anYJLTYL2BTwZYdDu9oAqL21PhI0VPylz9+r9yUgfrBVEUZw5kwbBF1ih3AnbNpHQx6i8SvLruc5NehKHM9gGUWBrWx3ZfZTjT8USsNdt0epv6wddG8eaL8BHZDQ1DVqED876EhVxsIZNIdNQ5v1ZZGuuge85OO8ELJtiJf7o7WBJHW21rRyHsxWPOO50TY7u89LNgu79BDXIxdTg2kppwfKN39zwVLSshdvU6AUtSIXm4SG2jHyAC9AzpQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.003726, 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 Tue, Apr 01, 2025 at 10:10:03AM +0200, David Hildenbrand wrote: > On 31.03.25 10:13, Baoquan He wrote: > > --- a/mm/gup.c > > +++ b/mm/gup.c > > @@ -2207,8 +2207,8 @@ size_t fault_in_safe_writeable(const char __user *uaddr, size_t size) > > } while (start != end); > > mmap_read_unlock(mm); > > - if (size > (unsigned long)uaddr - start) > > - return size - ((unsigned long)uaddr - start); > > + if (size > start - (unsigned long)uaddr) > > + return size - (start - (unsigned long)uaddr); > > return 0; > > } > > EXPORT_SYMBOL(fault_in_safe_writeable); > > Can we instead just use the uaddr and start variables like in > fault_in_readable? > > That is, turn "start" into a const and adjust uaddr instead. Yes, I think that would be much cleaner. Otherwise, this looks good to me. -- Oscar Salvador SUSE Labs