From: Rich Felker <dalias@libc.org>
To: Zhang Tianci <zhangtianci1@huawei.com>
Cc: musl@lists.openwall.com, yunlong.song@huawei.com
Subject: Re: [musl] [PATCH] stdio: Fix fdopen bug
Date: Tue, 18 Feb 2020 22:44:47 -0500 [thread overview]
Message-ID: <20200219034447.GB1663@brightrain.aerifal.cx> (raw)
In-Reply-To: <20200219023729.37349-1-zhangtianci1@huawei.com>
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 <zhangtianci1@huawei.com>
> ---
> 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
next prev parent reply other threads:[~2020-02-19 3:46 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-19 2:37 Zhang Tianci
2020-02-19 3:44 ` Rich Felker [this message]
2020-02-19 6:47 zhangtianci
2020-02-19 14:16 ` Rich Felker
2020-02-19 14:20 ` Jens Gustedt
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200219034447.GB1663@brightrain.aerifal.cx \
--to=dalias@libc.org \
--cc=musl@lists.openwall.com \
--cc=yunlong.song@huawei.com \
--cc=zhangtianci1@huawei.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://git.vuxu.org/mirror/musl/
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).