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Message-ID: <20200219023729.37349-1-zhangtianci1@huawei.com>
Date: Wed, 19 Feb 2020 10:37:29 +0800
From: Zhang Tianci <zhangtianci1@...wei.com>
To: <musl@...ts.openwall.com>
CC: <zhangtianci1@...wei.com>, <yunlong.song@...wei.com>
Subject: [PATCH] stdio: Fix fdopen bug
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@...wei.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
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