From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757066AbcLAKQR (ORCPT ); Thu, 1 Dec 2016 05:16:17 -0500 Received: from mail-wj0-f181.google.com ([209.85.210.181]:33510 "EHLO mail-wj0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756277AbcLAKPO (ORCPT ); Thu, 1 Dec 2016 05:15:14 -0500 From: Miklos Szeredi To: Al Viro Cc: linux-unionfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [PATCH 5/8] ovl: intercept read_iter Date: Thu, 1 Dec 2016 11:15:00 +0100 Message-Id: <1480587303-25088-6-git-send-email-mszeredi@redhat.com> X-Mailer: git-send-email 2.5.5 In-Reply-To: <1480587303-25088-1-git-send-email-mszeredi@redhat.com> References: <1480587303-25088-1-git-send-email-mszeredi@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ...in order to handle the corner case when the file is copyied up after being opened read-only. Can be verified with the following script: - 8< - - - - - 8< - - - - - 8< - - - - - 8< - - - - cd / rm -rf /tmp/ovl-rorw-test mkdir /tmp/ovl-rorw-test cd /tmp/ovl-rorw-test mkdir -p mnt lower upper work echo baba > lower/foo mount -t overlay overlay -olowerdir=lower,upperdir=upper,workdir=work mnt exec 3< mnt/foo echo bubu > mnt/foo cat <&3 exec 3>&- umount mnt - 8< - - - - - 8< - - - - - 8< - - - - - 8< - - - - Correct output is "bubu", incorrect output is "baba". Signed-off-by: Miklos Szeredi --- fs/overlayfs/inode.c | 29 ++++++++++++++++++++++++++++- 1 file changed, 28 insertions(+), 1 deletion(-) diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c index e98e3323c330..a2d5b3d03e14 100644 --- a/fs/overlayfs/inode.c +++ b/fs/overlayfs/inode.c @@ -12,6 +12,7 @@ #include #include #include +#include #include #include "overlayfs.h" @@ -368,6 +369,29 @@ void ovl_cleanup_fops_htable(void) __ofop->orig_fops->call; \ }) +static bool ovl_file_is_lower(struct file *file) +{ + return !OVL_TYPE_UPPER(ovl_path_type(file->f_path.dentry)); +} + +static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *to) +{ + struct file *file = iocb->ki_filp; + ssize_t ret; + + if (likely(ovl_file_is_lower(file))) + return OVL_CALL_REAL_FOP(file, read_iter(iocb, to)); + + file = filp_clone_open(file); + if (IS_ERR(file)) + return PTR_ERR(file); + + ret = vfs_iter_read(file, to, &iocb->ki_pos); + fput(file); + + return ret; +} + static struct ovl_fops *ovl_fops_find(const struct file_operations *orig) { struct ovl_fops *ofop; @@ -406,8 +430,11 @@ static struct ovl_fops *ovl_fops_get(struct file *file) ofop->magic = OVL_FOPS_MAGIC; ofop->orig_fops = fops_get(orig); + /* Intercept these: */ + if (orig->read_iter) + ofop->fops.read_iter = ovl_read_iter; + /* These will need to be intercepted: */ - ofop->fops.read_iter = orig->read_iter; ofop->fops.mmap = orig->mmap; ofop->fops.fsync = orig->fsync; -- 2.5.5