[Bug 26022] New: futimesat and utimensat handle NULL filenames

[Bug 26022] New: futimesat and utimensat handle NULL filenames

[bugzilla-daemon-590EEB7GvNiWaY/ihj7yzEB+6BGkLq7r]

https://bugzilla.kernel.org/show_bug.cgi?id=26022

           Summary: futimesat and utimensat handle NULL filenames
           Product: Documentation
           Version: unspecified
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: man-pages
        AssignedTo: documentation_man-pages-ztI5WcYan/vQLgFONoPN62D2FQJk+8+b@public.gmane.org
        ReportedBy: vapier-aBrp7R+bbdUdnm+yROfE0A@public.gmane.org
        Regression: No


if you pass futimesat or utimensat a NULL path, the functions will operate on
the fd as given.  in which case it can be either a fd for a directory or a
file.

for example, the two calls to futimesat() below will do the same thing:
#include <fcntl.h>
#include <stdio.h>
int main() {
    int fd = open("f", O_CREAT|O_RDWR, 0777);
    printf("futimesat = %i\n", futimesat(fd, NULL, NULL));
    printf("futimesat = %i\n", futimesat(AT_FDCWD, "f", NULL));
    return 0;
}

same behavior can be observed with utimensat(), but it seems only at the Linux
syscall level.  the POSIX/C library level will reject a NULL filename with
errno==EINVAL, but the Linux kernel will treat the dirfd as an fd.  funny
enough, while glibc rejects pathname==NULL at its ABI, it relies on the Linux
ABI to accept pathname==NULL while implementing other functions.

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[Bug 26022] futimesat and utimensat handle NULL filenames

[bugzilla-daemon-590EEB7GvNiWaY/ihj7yzEB+6BGkLq7r]

https://bugzilla.kernel.org/show_bug.cgi?id=26022

Michael Kerrisk <mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |INVALID
             Status|NEW                         |RESOLVED
                 CC|                            |mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org

--- Comment #1 from Michael Kerrisk <mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> ---
Mike,

The utimensat() behavior is discussed under NOTES in its man page.

The futimesat() behavior is discssed under NOTES in its man page.

So, I'm closing as invalid. If you think something is still missing, please
reopen and let me know what it is..

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