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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> 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-Disposition: inline In-Reply-To: X-Spam-Score: -4.30 X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-0.990]; MIME_GOOD(-0.10)[text/plain]; FROM_HAS_DN(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; ARC_NA(0.00)[]; TO_DN_SOME(0.00)[]; MIME_TRACE(0.00)[0:+]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_TLS_ALL(0.00)[]; MISSING_XM_UA(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; RCPT_COUNT_FIVE(0.00)[6]; RCVD_COUNT_TWO(0.00)[2]; RCVD_VIA_SMTP_AUTH(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,localhost.localdomain:mid] X-Spam-Flag: NO X-Spam-Level: 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