New: futimesat and utimensat handle NULL filenames

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/[email protected]
ReportedBy: [email protected]
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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https://bugzilla.kernel.org/show_bug.cgi?id=26022

Michael Kerrisk <[email protected]> changed:

What |Removed |Added
----------------------------------------------------------------------------

         Resolution|---                         |INVALID
             Status|NEW                         |RESOLVED
                 CC|                            |[email protected]

--- Comment #1 from Michael Kerrisk <[email protected]> --- 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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