From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-3.0 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED,RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL autolearn=ham autolearn_force=no version=3.4.2 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by inbox.vuxu.org (OpenSMTPD) with SMTP id d497f11f for ; Wed, 19 Feb 2020 03:46:19 +0000 (UTC) Received: (qmail 19732 invoked by uid 550); 19 Feb 2020 03:46:17 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Reply-To: musl@lists.openwall.com Received: (qmail 19557 invoked from network); 19 Feb 2020 03:45:10 -0000 Date: Tue, 18 Feb 2020 22:44:47 -0500 From: Rich Felker To: Zhang Tianci Cc: musl@lists.openwall.com, yunlong.song@huawei.com Message-ID: <20200219034447.GB1663@brightrain.aerifal.cx> References: <20200219023729.37349-1-zhangtianci1@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200219023729.37349-1-zhangtianci1@huawei.com> User-Agent: Mutt/1.5.21 (2010-09-15) Subject: Re: [musl] [PATCH] stdio: Fix fdopen bug On Wed, Feb 19, 2020 at 10:37:29AM +0800, Zhang Tianci wrote: > Currently, in musl the fdopen doesn't check the consistence between > fd's mode and corresponding file's mode. > > For example, > > int fd = open("file1", O_RDONLY); > FILE *f = fdopen(fd, "W") > > In musl, above code will be Okay. > While according to POSIX, above code (fdopen) will return EINVAL. > > Signed-off-by: Zhang Tianci > --- > src/stdio/__fdopen.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/src/stdio/__fdopen.c b/src/stdio/__fdopen.c > index 116e78e..23c4ffd 100644 > --- a/src/stdio/__fdopen.c > +++ b/src/stdio/__fdopen.c > @@ -26,6 +26,16 @@ FILE *__fdopen(int fd, const char *mode) > /* Impose mode restrictions */ > if (!strchr(mode, '+')) f->flags = (*mode == 'r') ? F_NOWR : F_NORD; > > + int fd_flag = __syscall(SYS_fcntl, fd, F_GETFL); > + > + if (fd_flag == -1) return 0; > + > + if (((fd_flag & O_ACCMODE) == O_RDONLY && !(f->flags & F_NORD)) || > + ((fd_flag & O_ACCMODE) == O_WRONLY && !(f->flags & F_NOWR))) { > + errno = EINVAL; > + return 0; > + } > + > /* Apply close-on-exec flag */ > if (strchr(mode, 'e')) __syscall(SYS_fcntl, fd, F_SETFD, FD_CLOEXEC); > > -- > 2.17.1 Per POSIX this is a "may fail" not a "shall fail". Testing for this is more costly (see added code/syscalls in the patch) and serves no purpose, which is why it's not done. Rich