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Tue, 01 Dec 2020 21:22:37 +0000 Received: from pps.filterd (userp3030.oracle.com [127.0.0.1]) by userp3030.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 0B1LBKsq163826; Tue, 1 Dec 2020 21:22:36 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by userp3030.oracle.com with ESMTP id 3540fxknej-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 01 Dec 2020 21:22:36 +0000 Received: from abhmp0011.oracle.com (abhmp0011.oracle.com [141.146.116.17]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 0B1LMYVl018071; Tue, 1 Dec 2020 21:22:35 GMT Received: from [192.168.2.112] (/50.38.35.18) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 01 Dec 2020 13:22:34 -0800 Subject: Re: [RFC PATCH 01/13] fs/userfaultfd: fix wrong error code on WP & !VM_MAYWRITE To: Nadav Amit , linux-fsdevel@vger.kernel.org Cc: Nadav Amit , Jens Axboe , Andrea Arcangeli , Peter Xu , Alexander Viro , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20201129004548.1619714-1-namit@vmware.com> <20201129004548.1619714-2-namit@vmware.com> From: Mike Kravetz Message-ID: <3af643ec-b392-617c-cd4e-77db0cba24bd@oracle.com> Date: Tue, 1 Dec 2020 13:22:32 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: <20201129004548.1619714-2-namit@vmware.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9822 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 malwarescore=0 suspectscore=0 phishscore=0 mlxlogscore=999 adultscore=0 mlxscore=0 bulkscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2012010129 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9822 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 lowpriorityscore=0 clxscore=1011 bulkscore=0 mlxlogscore=999 phishscore=0 malwarescore=0 spamscore=0 adultscore=0 mlxscore=0 priorityscore=1501 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2012010129 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: On 11/28/20 4:45 PM, Nadav Amit wrote: > From: Nadav Amit > > It is possible to get an EINVAL error instead of EPERM if the following > test vm_flags have VM_UFFD_WP but do not have VM_MAYWRITE, as "ret" is > overwritten since commit cab350afcbc9 ("userfaultfd: hugetlbfs: allow > registration of ranges containing huge pages"). > > Fix it. > > Cc: Mike Kravetz > Cc: Jens Axboe > Cc: Andrea Arcangeli > Cc: Peter Xu > Cc: Alexander Viro > Cc: io-uring@vger.kernel.org > Cc: linux-fsdevel@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > Cc: linux-mm@kvack.org > Fixes: cab350afcbc9 ("userfaultfd: hugetlbfs: allow registration of ranges containing huge pages") > Signed-off-by: Nadav Amit > --- > fs/userfaultfd.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c > index 000b457ad087..c8ed4320370e 100644 > --- a/fs/userfaultfd.c > +++ b/fs/userfaultfd.c > @@ -1364,6 +1364,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx, > if (end & (vma_hpagesize - 1)) > goto out_unlock; > } > + ret = -EPERM; > if ((vm_flags & VM_UFFD_WP) && !(cur->vm_flags & VM_MAYWRITE)) > goto out_unlock; > Thanks! We should return EPERM in that case. However, the check for VM_UFFD_WP && !VM_MAYWRITE went in after commit cab350afcbc9. I think it is more accurate to say that the issue was introduced with commit 63b2d4174c4a ("Introduce the new uffd-wp APIs for userspace."). The convention in userfaultfd_register() is that the return code is set before testing condition which could cause return. Therefore, when 63b2d4174c4a added the VM_UFFD_WP && !VM_MAYWRITE check, it should have also added the 'ret = -EPERM;' statement. With changes to commit message and Fixes tag, Reviewed-by: Mike Kravetz -- Mike Kravetz