On Saturday 27 December 2008 11:46:03 Mitar wrote:
> Hi!
>
> I discovered that open syscall with only O_APPEND fails with
> "permission denied" if an user does not have rights to write to a file
> (what is normal) even if it is root (what is a surprise). For example,
> if I have a file owned by www:www and with 644 permissions root cannot
> do open("testfile", O_APPEND) call. If I change ownership of I change
> permission to for example 666, call succeedes.
>
> This works on Linux (Debian). So this is a feature? Or a bug?
>
> (I discovered that because htpasswd failed to add new
> username/password pair (ran as root) to a file owner by www.)
>
> Checked on FreeBSD 7.0-STABLE.
Can't reproduce:
$ ls -al test.txt
-rw-r--r-- 1 www www 33 Dec 27 15:12 test.txt
$ sudo ./open
test.txt opened as fd 3
$ cat test.txt
this file
cannot be appended to
$ cat -n open.c
1 #include <sys/types.h>
2 #include <sys/uio.h>
3 #include <unistd.h>
4 #include <stdio.h>
5 #include <fcntl.h>
6 #include <err.h>
7 #include <sysexits.h>
8
9 int main(void)
10 {
11 const char fname[] = "test.txt";
12 const char txt[] = "cannot be appended to\n";
13 int fd;
14
15 fd = open(fname, O_WRONLY|O_APPEND);
16 if( fd < 0 )
17 err(EX_NOINPUT, "Failed to open %s", fname);
18
19 printf("%s opened as fd %i\n", fname, fd);
20 if( write(fd, txt, sizeof(txt)) < 0 )
21 err(EX_DATAERR, "write()");
22 close(fd);
23 return EX_OK;
24 }
--
Mel
Problem with today's modular software: they start with the modules
and never get to the software part.
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