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SubjectRe: [Bugme-new] [Bug 14832] New: futimens (AT_FDCWD, arg) should fail

(switched to email. Please respond via emailed reply-to-all, not via the
bugzilla web interface).

On Fri, 18 Dec 2009 16:08:29 GMT
bugzilla-daemon@bugzilla.kernel.org wrote:

> http://bugzilla.kernel.org/show_bug.cgi?id=14832
>
> Summary: futimens (AT_FDCWD, arg) should fail
> Product: File System
> Version: 2.5
> Platform: All
> OS/Version: Linux
> Tree: Mainline
> Status: NEW
> Severity: normal
> Priority: P1
> Component: Other
> AssignedTo: fs_other@kernel-bugs.osdl.org
> ReportedBy: ebb9@byu.net
> Regression: No
>
>
> According to POSIX 2008, futimens() shall fail with EBADF if fd is not a valid
> file descriptor. AT_FDCWD, being negative, falls into this category. Yet this
> program mistakenly changes the timestamps of the current directory, then
> aborts:
>
> #include <sys/stat.h>
> #include <fcntl.h>
> #include <errno.h>
> #include <stdlib.h>
> int
> main ()
> {
> if (futimens (AT_FDCWD, NULL) != -1 || errno != EBADF)
> abort ();
> }
>
> Since futimens is a library call on top of utimensat, the fix is to add a
> special case to the utimensat syscall that fails with EBADF if fd is negative
> when path is NULL.
>

Confused.

: long do_utimes(int dfd, char __user *filename, struct timespec *times, int flags)
: {
: int error = -EINVAL;
:
: if (times && (!nsec_valid(times[0].tv_nsec) ||
: !nsec_valid(times[1].tv_nsec))) {
: goto out;
: }
:
: if (flags & ~AT_SYMLINK_NOFOLLOW)
: goto out;
:
: if (filename == NULL && dfd != AT_FDCWD) {
: struct file *file;
:
: if (flags & AT_SYMLINK_NOFOLLOW)
: goto out;
:
: file = fget(dfd);
: error = -EBADF;
: if (!file)
: goto out;
:

afacit, if filename==NULL and dfd==-1 then fget() will return NULL and
the syscall returns -EBAFD.

Your report doesn't tell us what kernel version you're testing. We did
fix a few things ni this area, but it was a long time ago.



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