Re: [PATCH] Use xattr (Linux) in qcopy-acl.c

From: Bruno Haible <bruno@clisp.org>
To: bug-gnulib@gnu.org,
	Ondrej Valousek <ondrej.valousek.xm@renesas.com>,
	Paul Eggert <eggert@cs.ucla.edu>
Subject: Re: [PATCH] Use xattr (Linux) in qcopy-acl.c
Date: Thu, 05 Jan 2023 09:56:09 +0100	[thread overview]
Message-ID: <2520566.AOvM4ru3NT@nimes> (raw)
In-Reply-To: <e46d9ca3-600d-aa46-809f-89e3b9b9879b@cs.ucla.edu>

Paul Eggert wrote:
> I see a problem in linking. With this change, programs using the 
> qcopy-acl module will link to both $(LIB_ACL) and $(LIB_XATTR), even 
> though they do not need to link with $(LIB_ACL). Perhaps you can fix 
> this by fixing the Link sections of the relevant modules to use 
> $(LIB_HAS_ACL) instead of $(LIB_ACL).

Good point.

But I would call this variable $(COPY_ACL_LIB). Our convention for these
variables is generally
  - $(LIBFOO) or $(LIB_FOO) for the library -lfoo (or empty if nonexistent
    or not needed),
  - $(MODULE_LIB) for the libraries needed by a given module. For example,
    we have
      $(GETADDRINFO_LIB)
      $(GETHOSTNAME_LIB)
      $(GETLOADAVG_LIBS)
      $(INET_NTOP_LIB)
      $(PTY_LIB)
      $(YIELD_LIB)

> Also, come to think of it, is there a security issue between the 
> chmod_or_fchmod call, and the attr_copy_fd call? That is, could the file 
> temporarily be set to too-generous permissions, between the two calls?

For the use of qcopy_acl by copy-file.c, there is no issue, because when
qcopy_acl gets called, the new file has mode 0600 and the owner and group
are already set. So, this is not too generous.

But for the uses of copy_acl in coreutils, I can't really tell...

Bruno