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[75.142.250.213]) by smtp.gmail.com with ESMTPSA id i8sm11202871qtr.90.2020.07.03.12.24.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 03 Jul 2020 12:24:01 -0700 (PDT) Subject: Re: [PATCH v2] mm: initialize return of vm_insert_pages To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20200703155354.29132-1-trix@redhat.com> <20200703120436.4031b4ea23e28a3babca3d2d@linux-foundation.org> From: Tom Rix Message-ID: <3fdd71e8-d149-888c-b7de-99e5f68871a0@redhat.com> Date: Fri, 3 Jul 2020 12:23:59 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200703120436.4031b4ea23e28a3babca3d2d@linux-foundation.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/3/20 12:04 PM, Andrew Morton wrote: > On Fri, 3 Jul 2020 08:53:54 -0700 trix@redhat.com wrote: > >> From: Tom Rix >> >> clang static analysis reports a garbage return >> >> In file included from mm/memory.c:84: >> mm/memory.c:1612:2: warning: Undefined or garbage value returned to caller [core.uninitialized.UndefReturn] >> return err; >> ^~~~~~~~~~ >> >> The setting of err depends on a loop executing. >> So initialize err. >> >> ... >> >> --- a/mm/memory.c >> +++ b/mm/memory.c >> @@ -1601,7 +1601,7 @@ int vm_insert_pages(struct vm_area_struct *vma, unsigned long addr, >> return insert_pages(vma, addr, pages, num, vma->vm_page_prot); >> #else >> unsigned long idx = 0, pgcount = *num; >> - int err; >> + int err = -EINVAL; >> >> for (; idx < pgcount; ++idx) { >> err = vm_insert_page(vma, addr + (PAGE_SIZE * idx), pages[idx]); > If a caller were to ask vm_insert_pages() to insert zero pages, I > suspect we should just return zero and set *num to zero. That would be v1 of the patch. For the loop to not execute *num/pgcount is initially 0, and *num = pgcount - idx is 0 on exit.   >