On 11/25/20 2:27 PM, Mathias Rav wrote: > Linux kernel commit aae8a97d3ec30788790d1720b71d76fd8eb44b73 > (part of kernel release v2.6.39) added a check to disallow creating a > hardlink to an unlinked file. > > Signed-off-by: Mathias Rav <m@xxxxxxxxxxxxx> Thanks, Matthias. Patch applied. > --- > The manual page already describes the trick of using AT_SYMLINK_FOLLOW > as an alternative to AT_EMPTY_PATH, and for AT_EMPTY_PATH the manual > page already notes that it "will generally not work if the file has a > link count of zero". However, the precise error (ENOENT) is not mentioned, > and the error case isn't mentioned in the ERRORS section at all. > > This makes it easy to overlook the fact that the AT_SYMLINK_FOLLOW > trick on /proc/self/fd/NN won't work on deleted files, as evidenced by > the follow message (which turns up when googling "linkat deleted ENOENT"): > https://groups.google.com/g/linux.kernel/c/zZO4lqqwp64 I think the above piece is actually worth including in the commit message, so I added it. Thanks, Michael > man2/link.2 | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/man2/link.2 b/man2/link.2 > index 1e7b2efd8..202119c6e 100644 > --- a/man2/link.2 > +++ b/man2/link.2 > @@ -318,6 +318,10 @@ open(path, O_TMPFILE | O_EXCL, mode); > .IP > See > .BR open (2). > +.B ENOENT > +An attempt was made to link to a > +.I /proc/self/fd/NN > +file corresponding to a file that has been deleted. > .TP > .B ENOENT > .I oldpath > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/
